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Uncertainty and Probability—in Halakha, in Thought, and in General—Lesson 23 – Rabbi Michael Abraham

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This transcript was produced automatically using artificial intelligence. There may be inaccuracies in the transcribed content and in speaker identification.

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Table of Contents

  • Bayes' formula and the distinction between probabilities
  • Decomposing \(P(B)\) and analyzing \(P(\neg A\mid B)\)
  • Begging the question and the weight of prior assumptions
  • “Tabula rasa” and the Bayesian reinforcement of the physico-theological argument
  • The plausibility of the complexity assumption, the second law, and distinguishing it from the question of suffering
  • Entropy and objective measures of complexity
  • Biases, dismissing evidence for the existence of God, and Beit Hillel and Beit Shammai
  • The topic of “this one benefits and that one does not lose” in Bava Kamma and its connection to bias and evaluation
  • Rabbi Shimon Shkop’s interpretation and the principle of appreciation as a condition for learning
  • The role of mathematics: not proving God, but sharpening the probabilistic question
  • Evolution, the “God of the gaps,” and the move from life to the laws of nature
  • Conditional versus absolute probability in the context of the laws of nature
  • The example of “the burden of proof is on the claimant” and the distinction between presumptions and probability
  • Credibility, dependence between variables, and cases of approximation
  • Conclusion and a remark about the rhetorical value of aggadic literature

Summary

Overview

The speaker sharpens the distinction between absolute probability and conditional probability, and between \(P(B\mid A)\) and \(P(A\mid B)\), through a Bayesian formulation of the physico-theological argument. He argues that many mistakes in discussions about the existence of God come from mixing up probabilistic questions and from unconscious prior assumptions. He shows how extreme prior assumptions on either side simply bring us back to begging the question, but that if one starts with \(P(A)=P(\neg A)=\tfrac12\) and assumes that \(P(B\mid \neg A)\) is very small, then \(P(\neg A\mid B)\) comes out small and therefore \(P(A\mid B)\) comes out large. He connects this to the need to define the statistical question correctly, to trust in the assumptions, and to psychological and character-based biases that can mislead even very intelligent people, illustrating this through Talmudic topics and the principle of “charity” in listening to an opponent’s argument.

Bayes' formula and the distinction between probabilities

The speaker defines \(A\) as “God exists” and \(B\) as “a complex world exists,” and distinguishes between \(P(B\mid A)\) and \(P(A\mid B)\), and between the absolute probability \(P(A)\) and the conditional probability given the world. He mentions Bayes' formula as a way to convert between reversed conditional probabilities through the equality \(P(A\cap B)=P(B\mid A)P(A)=P(A\mid B)P(B)\). He criticizes Ilam Gross’s claim that \(P(B\mid A)=1\), arguing that there is no way to calculate that, because it depends on the will of the Holy One, blessed be He, and not on a random event.

Decomposing \(P(B)\) and analyzing \(P(\neg A\mid B)\)

The speaker writes \(P(B)\) as the sum \(P(B\mid \neg A)P(\neg A)+P(B\mid A)P(A)\), and substitutes this into Bayes' formula for the event \(\neg A\) in order to get an expression for \(P(\neg A\mid B)\). He takes as a basic assumption of the physico-theological argument that \(P(B\mid \neg A)\) is very small, because a complex world does not arise spontaneously without a creating cause. He emphasizes that \(P(\neg A)\), \(P(B\mid A)\), and \(P(A)\) are not known, and therefore the conclusion depends heavily on the prior assumptions one feeds into the calculation.

Begging the question and the weight of prior assumptions

The speaker shows that if one adopts “Gross’s glasses” and assumes in advance that \(P(A)\) is extremely tiny or zero, then one immediately gets \(P(\neg A\mid B)\approx 1\), meaning there is no God, because the denominator collapses into the numerator. He shows that the opposite assumption, \(P(\neg A)=0\), symmetrically leads to the conclusion that \(P(\neg A\mid B)=0\), meaning there is a God. He concludes that one cannot get anywhere if each side fixes the result in advance on an a priori basis, and that this illustrates the fact that probabilistic calculation is mathematical, but the probabilities fed into it are products of one’s worldview and foundational assumptions.

“Tabula rasa” and the Bayesian reinforcement of the physico-theological argument

The speaker proposes starting from a “fair fight” in which \(P(A)=P(\neg A)=\tfrac12\), and then checking whether the datum \(B\) raises the probability of God's existence above one-half. He simplifies the formula to \(P(\neg A\mid B)=\frac{P(B\mid \neg A)}{P(B\mid \neg A)+P(B\mid A)}=\frac{1}{1+\frac{P(B\mid A)}{P(B\mid \neg A)}}\), and argues that since \(P(B\mid \neg A)\) is very small, the denominator is large and therefore \(P(\neg A\mid B)\) is small. He concludes that on this approach one gets “if there is a complex world, then there is God” without assuming in advance that \(P(A)\) is high, and he presents this as the essence of the physico-theological argument and as a mathematical sharpening of the simple logic that “any ordinary person understands.”

The plausibility of the complexity assumption, the second law, and distinguishing it from the question of suffering

The speaker frames the central assumption as the claim that a complex world does not arise on its own, and in mathematical language this is the claim that \(P(B\mid \neg A)\) is very small. He argues that this assumption sounds plausible to him, among other reasons “because of the second law of thermodynamics,” and stresses that every logical argument rests on assumptions, and one may dispute them, but their plausibility has to be examined. He distinguishes between complexity and suffering, arguing that the problem of suffering is a separate claim that comes to challenge the existence of God and is unrelated to the question of entropy or complexity.

Entropy and objective measures of complexity

The speaker defines entropy as a quantity in physics that measures the degree of order or complexity, and argues that it is an objective measure that does not depend on “the eye of the beholder.” He responds to the atheistic claim that complexity is perceptual by saying that there are objective scientific calculations showing that the world is “special.” He explains this “specialness” in terms of a lottery of worlds arranged according to their level of order, and argues that our world is found “very high up,” and therefore the number of worlds with that sort of order is “a tiny number.”

Biases, dismissing evidence for the existence of God, and Beit Hillel and Beit Shammai

The speaker argues that there is a tendency to dismiss any evidence for the existence of God, and therefore people throw out arguments without seriously thinking about what the other person said. He quotes the Talmud in Eruvin about the ruling following Beit Hillel “because they were gentle and humble, and they would state the words of Beit Shammai before their own,” and presents this as a model for weighing the opponent’s claim before forming one’s own position. He concludes that the ability to arrive at correct conclusions depends not only on sharpness but also on character traits, and that sometimes sharpness itself leads to dismissiveness, failure to listen, and the ability to “prove anything,” and therefore, “the sharper the mouth, the greater the error.”

The topic of “this one benefits and that one does not lose” in Bava Kamma and its connection to bias and evaluation

The speaker brings the passage in Bava Kamma 20a about the question, “If someone lives in another person’s courtyard without his knowledge, must he pay him rent or not?”, and presents the analysis of “this one benefits and that one does not lose” as opposed to “this one benefits and that one loses.” He describes Rami bar Hama’s reaction, “It is in the Mishnah,” and his demand, “When you serve me, then [I will explain it],” and Rava’s statement, “How sickly and weak is a man whose master helps him,” referring to the fact that the Mishnah seemingly is not comparable, because it is a case of “this one benefits and that one loses.” He presents the Talmud’s answer, “Ordinary produce in the public domain is considered owner-abandoned,” as an explanation of how the case does indeed become comparable to “this one benefits and that one does not lose,” and stresses that this seems strange at first and therefore requires a willingness to think twice.

Rabbi Shimon Shkop’s interpretation and the principle of appreciation as a condition for learning

The speaker attributes to Rabbi Shimon Shkop, in the introduction to Shaarei Yosher, the idea that “when you serve me” tests whether the student values the rabbi, because without appreciation he will not learn anything new from him. He presents the logic that if there is no appreciation, then whatever one already agrees with is accepted anyway, and whatever one disagrees with is immediately thrown out, so there is no real change. He uses this to explain how Rav Chisda, who had served Rami bar Hama, was prepared to accept an answer that at first sounded implausible, whereas Rava dismissed it contemptuously, and he formulates this as the “principle of charity,” namely, presenting the opponent’s argument in the best possible way before criticizing it.

The role of mathematics: not proving God, but sharpening the probabilistic question

The speaker says that his purpose is not to prove that there is a God by means of mathematics, but to show how important it is to define the probabilistic question correctly, such as \(P(B\mid A)\) versus \(P(A\mid B)\), or \(P(\neg A\mid B)\). He argues that mathematics helps show just how much the starting point affects a statistical calculation, and how questions that appear similar can in fact yield completely different results. He concludes that the physico-theological argument emerges in a “refined and mathematical” form as a very high probability for the existence of God given a world, subject to the assumption that \(P(B\mid \neg A)\) is very small.

Evolution, the “God of the gaps,” and the move from life to the laws of nature

The speaker presents the biologico-theological argument about the formation of life, and then the role of evolution as a natural mechanism that undermines the claim that life could not arise without a guiding hand. He criticizes the “God of the gaps” approach and argues that faith should not be based on scientific ignorance, because gaps close through research. He shifts the discussion from the formation of life to the formation of the laws of nature that make life possible, and argues that even if a scientific explanation for those laws is found, it will rely on “meta-laws,” producing a regression of “turtles all the way down,” so that the question about the basic law — “who created that law?” — remains in principle.

Conditional versus absolute probability in the context of the laws of nature

The speaker formulates the evolutionary claim as increasing \(P(\text{life}\mid \text{certain laws})\) to almost one, but argues that this is only a conditional description. He claims that the decisive question is \(P(\text{laws that allow life})\), meaning the absolute probability of getting such a special system of laws, and there the chance is very small, so there is evidence for the existence of God. He says that here an “opposite mistake” occurs, where people focus on the conditional probability and ignore the tiny prior, and he illustrates this also in discussions about infinities through the distinction between the infinity of the natural numbers and the infinity of the real numbers, along with the claim that “the chance is still zero.”

The example of “the burden of proof is on the claimant” and the distinction between presumptions and probability

The speaker argues that the common explanation of the rule “the burden of proof is on the claimant” as a probabilistic presumption that “whatever is in a person’s possession is his” is mistaken, because it replaces an absolute probability over all objects with a conditional probability over the subset of objects involved in legal dispute. He claims that among all objects, most are indeed in the hands of their owners, but given a legal dispute there is no reason to assume that the claimant is more likely to be lying than the possessor, and therefore the probability is “fifty-fifty.” He explains that the correct justification is legal: a religious court does not intervene without proof, so the situation remains as it is, and not because the possessor has a probabilistic advantage.

Credibility, dependence between variables, and cases of approximation

The speaker rejects a proposal to “multiply” probabilities of credibility with the general statistics, and argues that one does not multiply here because the variables are dependent. He explains that the possibility that the sides are mistaken rather than lying changes the assumptions, and gives the example that a situation in which “there are no liars” would change the relevance of the general statistics. He says that in situations where there is concern for approximation, the law changes, and he gives the example of “migo in a case of approximation,” as well as identification of the dead and permitting agunot, as places where the concern is imagination rather than deceit.

Conclusion and a remark about the rhetorical value of aggadic literature

At the end, someone suggests that the speaker should deal more with aggadah, and he responds that the example he brought is a “narrative frame for Jewish law,” and that for him its main value is illustrative rather than a source for changing one’s position. He agrees that aggadic literature has rhetorical value that intensifies the human impact even when the conclusion was already clear in advance. He closes with the blessing, “Shabbat shalom and good tidings.”

Full Transcript

[Rabbi Michael Abraham] Last time I tried to demonstrate the meaning of conditional probability through a Bayesian look at the physico-theological argument — in other words, the arguments for the existence of God — but in a kind of formal sense, a statistical perspective. I introduced there what the physicist Ilam Gross argued in some article and in a debate we had. I explained the mistakes in what he said there and showed that basically his error was rooted in the fact that he didn’t distinguish — even though he wrote down that distinction, in practice when he made the argument he ignored it — the distinction between the probability that if there is a God then there is a complex world, and the probability that if there is a complex world then there is a God. Conditional probability of A given B, or B given A. And maybe also the difference between the absolute probability that there is a God and the conditional probability given that this is the world — that is, that there is a complex world — what is the chance that there is a God. Now, in order to sharpen that last distinction between conditional probability and full probability, I want to get to another formulation of that distinction, and there we’ll see several points more clearly. Okay, so I’ll remind you a bit of the notation so we can use it. So proposition A — you can see here — we have two propositions. A is the proposition “God exists,” B is the proposition “a complex world exists.” Okay? Now basically we have several probabilities that we can define here. P of A is the probability that God exists. P of B is the probability that a complex world exists — in our case that’s one, because we simply know there is a complex world, that’s given. Now there is the conditional probability P of B given A, meaning: if God exists, what is the probability that there will be a complex world? He claimed that this is one, one hundred percent, and I said that’s nonsense, there’s no such thing, you can’t calculate such a probability, there’s no way to know — it depends on the will of the Holy One, blessed be He, it’s not even a random variable. And the last probability, which is the one that interests us, is P of A given B — meaning, given that there is a complex world, what is the probability that there is a God, that God exists. Okay? So pay attention, I’m reminding you again of Bayes’ formula. Let’s go up for a moment — we saw it above. This is Bayes’ formula. It basically says that the probability that A and B both occur can be presented in two ways: either as the probability of B given A times the probability of A. Right? If A exists, and given A what is the probability that B also exists, then that product gives me the probability that both A and B hold. Likewise, the probability that B exists times the probability that if B exists then A also exists gives me the probability of both of them. So if those two are equal to each other, then we focused only on these two — yes, each of these expressions equals the expression on the left — so they are equal to each other as well. If they are equal to each other, you see, we have a way to move from one conditional probability to the reverse conditional probability. You see here this is P of B given A, and here it’s P of A given B. So now, if one of them is given to me, I can try to derive the other from it. Okay, that’s basically Bayes’ formula. And now the claim is as follows: I now want to use another way to calculate the probability P of B in general. In our case this is basically the probability that there is a complex world, but for us that’s one; I’m writing it now in a more general way, and I say this: P of B is P of B given not-A times P of not-A, plus P of B given A times P of A. Meaning there are two… there are two possibilities: either A is true or A is not true; there are no other possibilities. So now I ask: what is the probability that B exists if A is not true, plus the probability that B exists if A is true — together that is the total probability of B. Okay? So if I now plug this sum in place of P of B in Bayes’ formula, I now get this formula. So P of not-A given B equals P of B given not-A times P of not-A, divided by P of B. That’s Bayes’ formula. If here it says P of B, what I did is write Bayes’ formula where the event is not A rather than A. But that doesn’t matter, that’s also an event, I don’t care which one I choose. Now I just substitute in place of P of B this whole parenthetical expression. Okay? This is an identity; in place of that comes P of B. Why is that useful to me? Because now I can try to estimate what this probability actually is. What will this probability give me? Notice what is written here. This is the probability that, given the complex world before us, what is the probability that there is no God. After all, we know that given that there is no God, the chance of getting a complex world is tiny. Right? A complex world doesn’t arise by itself — in other words, something has to create it. So I formulated this last time, I said the probability of B given not-A is very, very small. I called it x, some very small quantity. But what interests me now is the reverse probability: P of not-A given B. Why? Because I’m asking the question: what is the probability that there is a God, not what is the probability that there is a world. So I’m saying: given that there is a world, what is the probability that there is no God? Okay? If I find that, I can find the probability that there is a God, because it is one minus that probability. Okay? The probability that there is a God and the probability that there is no God add up to one. So now I can calculate this thing. Now what happens? When I calculate this thing, I say: I basically have this equal to this fraction. You see? It’s in the… it’s a little hard to see it like this — this is the numerator, you see? And these big parentheses here are the denominator. Okay. Now notice which expressions appear here, what I know and what I don’t know. So here’s the situation: I have P of B given not-A. You see it? That’s the first expression. I can say something about that, right? If there is no God, what is the probability that there is a complex world? Tiny, a tiny x. I called it x, but it’s a very small quantity. Right? A complex world doesn’t arise spontaneously without someone creating it. Okay. Therefore this probability is a very small quantity. What is P of not-A? That’s the probability that there is no God. I have nothing to say about that, I don’t know. Okay? For now. Now what does it say here? P of B given not-A. That again is the quantity I know something about — it’s very small. P of not-A — I don’t know what it is, just like here, it’s exactly the same expression. Here there is P of B given A. Meaning: given that there is a God, what is the probability that there will be a world? I don’t know what it is. And P of A, the probability that there is a God, I also don’t know. Okay. So now look. I know that P of A plus P of not-A is one, right? The probability that there is a God plus the probability that there is no God is one. There are only two possibilities: either He exists or He doesn’t. The probabilities add up to one. Now let’s look for a moment at the denominator. I’m looking at this through Gross’s glasses. He claims that P of A is a very small quantity. The probability that there is a God is very small. He writes that there. Okay. So if P of A is very small, and P of B given not-A is also very small, then there’s a competition here between the two terms — both are very small — and one has to estimate each relative to the other. I have no way of doing that, I don’t know how to do it. If you assume that P of A is really, really, really zero, then okay, fine — then the probability, the result is one. Right? Let’s say P of A is zero. If you assume there is no God — clearly there is no God — then let’s say this is really zero, not just small. Then this drops out. Notice, you have numerator divided by denominator where the denominator is identical to the numerator. You see? The same thing. So the result is one. So the probability that there is no God… given a world… is one. In short, there is no God. But of course that’s only if I assumed that the probability of God’s existence is zero, or as tiny as can be. Okay? You understand that this is basically begging the question. Right? Given that I rule out a priori the probability of God’s existence, then the conditional probability that there is no God given that there is a world is also about one, or that there is a God is about zero. But that’s not much of a trick — if I assume there’s no chance that there is a God, obviously the result of the calculation will tell me that the probability of God’s existence is very small. We won’t get very far from that. Fine, so what should I assume? I’ll assume the opposite: that the probability that there is no God is zero. That’s my assumption — Ilam Gross’s opposite, my assumption is that the probability there is no God is zero — and then what comes out? This becomes zero. I have the numerator of this divided by the denominator of this, right? Now the probability that there is no God is zero, so basically this result comes out zero, right? It’s zero divided by zero plus something. So the result is zero, so the probability that there is no God is zero. If I assume what I want to prove — that the probability that there is a God is high — then obviously I will also get that the conditional probability that there is no God is very low, or in short I’ll get that there is a God. In short, you can’t get out of this, because each of us can simply assume what he wants to prove. Right? Whatever you assume will give you the result you get. Notice that this itself is a very important conclusion, because it shows us that our prior assumptions carry decisive weight when we do probabilistic calculations. We tend to think that a probability calculation is mathematics, which is true, but the probabilities themselves that I plug into the probabilistic calculation are a product of our perception of reality, of our assumptions. And therefore our assumptions affect the final result through the mathematics. If you assume there is no God, you’ll get that the physico-theological argument is worth nothing. If you assume there is a God, you’ll get that the physico-theological argument is wonderful. Thank you very much — that didn’t help me at all. So in short I will always get what I assumed. How can we nevertheless move forward? So here is a suggestion for how we can move forward. Let’s make the calculation as if we’re tabula rasa. We know nothing about God’s existence, so the simplest thing is to assume that P of A and P of not-A are both one-half. Okay? Equal chances that there is a God and that there is no God. Okay? This is a fair fight, right? I’m not assuming his assumption and I’m not assuming my assumption; I’m assuming that the prior probabilities are equal. And now I say: all this is just in the general probability. Now I say, fine, but now I have an additional piece of data: I am given a world, a complex world. Does that improve the probability of God’s existence, raise it above one-half? Right? That is really the question. Is the physico-theological argument worth anything? If it improves the probability, then the physico-theological argument is good, right? Because it basically says that even if in advance you assume nothing about God’s existence, after you do this Bayesian calculation of the physico-theological argument you’ll get that the probability of God’s existence is high, or that the probability of His nonexistence is low. Okay? So let’s see. If I set P of A equal to P of not-A, both equal to one-half, then look — notice: this is one-half and this is one-half and this is one-half. So of course they all cancel out, right? What I’m left with is basically P of B given not-A divided by P of B given not-A plus P of B given A. That’s what remains. Now you can divide numerator and denominator, and you get this. P of not-A given B — I remind you again what this is — the probability that there is no God given that there is a complex world, right? Not-A is no God, B is a complex world. Okay? What does that give? One divided by one plus P of B given A divided by P of B given not-A. Now what is P of B given A? Given that there is a God, what is the probability that there will be a world? I have no idea, no way of knowing, I don’t know. Okay? But what is P of B given not-A? What do I know about that? Very small, right? Given that there is no God, what is the probability that a complex world would come into being? Very small — that is the assumption of the physico-theological argument. So do you see what happens here? This is one plus some quantity divided by a very, very small quantity. That means we have a very large denominator. That means that one divided by that large denominator is a very small number. Or in other words, I got that this quantity is very small. What does that mean? That if there is a complex world, the probability that there is no God is small. Probably very small, in fact. Or in other words: if there is a complex world, then there is a God. Now notice, I got this without assuming in either direction. Meaning I did not assume that P of A, the probability that God exists, is high, and I also did not assume that the probability that He does not exist is high. I assumed that the probabilities are equal a priori. Let’s say that before I saw the world, the probability that there is or is not a God was fifty-fifty. Okay? For the sake of discussion. I don’t know, I can’t say anything about it. Given that the probabilities are fifty-fifty, this added piece of information that says there is a complex world tells me that the probability of God’s existence has increased dramatically relative to my prior assumption. That is the essence of the physico-theological argument, and it is an excellent argument. And this Bayesian calculation merely sharpens that same simple logic that any ordinary person understands even without mathematics. But the mathematics here helped me show you, first, just how much the starting point, or the foundational assumptions, affect a statistical calculation. How important it is to define well the probabilistic question that we are calculating. Is it P of B given A, P of A given B, P of not-A given B — in other words, these are questions that seem similar, but they are completely different questions, and the answers to them can be dramatically different. And then suddenly you get the physico-theological argument in a very distilled and mathematical form: simply, the probability of God’s existence is very close to one, very high, given that there is a world. Of course, all this is based on the assumption — but the assumption sounds very reasonable — that if there is no God, the probability that there exists a world, a complex world, is very small. A complex thing doesn’t arise on its own, right? When I formulate the physico-theological argument in non-mathematical language, in its usual philosophical formulation, the central assumption of the argument is that a complex world does not just come about like that, right? Without someone assembling it. In mathematical language, what that means is that P of B given not-A is a very small quantity. Meaning, the probability that there exists a world, assuming there is no God — a complex world, assuming there is no God — is very small. Now if we accept this reasonable assumption — and in my view it is a very reasonable assumption — then the physico-theological argument is excellent. Of course, someone can come along and say: I don’t accept that assumption, as with any logical argument. And there are noises here.

[Speaker C] But isn’t that, again, begging the question?

[Rabbi Michael Abraham] No, it isn’t. Because here I didn’t assume — wait a second — here I didn’t assume that there is a high probability of God’s existence, and I also didn’t assume a low probability of God’s existence. I assumed that a priori the probabilities are equal.

[Speaker C] But if there is a complex world, there has to be a God. That’s basically the assumption.

[Rabbi Michael Abraham] No, the assumption was that if there is no God, then there won’t be a complex world, or the probability that there will be a complex world is very small.

[Speaker C] Well, that’s really our conclusion too.

[Rabbi Michael Abraham] True, but look — every logical argument is like that. A logical argument is always based on assumptions, and you can always dispute the assumptions and then reject the conclusion. Now you have to examine whether the assumptions are reasonable or not. Here that’s not the role of logic, and in my formulation not the role of statistics either. Think about what you think of that assumption. In my eyes it is a very reasonable assumption. The assumption that a complex thing does not arise on its own because of the second law of thermodynamics. So therefore, if I adopt this reasonable assumption, the conclusion is that there is a God. And that’s what the argument does. You can’t expect an argument to lead you to a conclusion that is not based on assumptions. There is no such thing; an argument always starts from assumptions. The whole question is whether the assumptions are reasonable assumptions. I think that assuming something like this is very reasonable. If someone insists and says he doesn’t accept it, fine, then no. An argument always appeals to someone who accepts its assumptions; there’s no way around that.

[Speaker D] What did we gain by moving from that assumption to the conclusion? I mean, how is this different from the joke about “and Abraham went”?

[Rabbi Michael Abraham] Every logical argument is no different from that joke. That’s obvious. But in practice, you see that people don’t notice — and there is a good proof here. After all, I could ask a general question about any logical argument, right? It’s Abraham and the hat. Any logical argument, basically, you could say: what good is it, the conclusion is contained within the assumptions. And the answer is that it really doesn’t help on the theoretical level, on the principled level, because the information in the conclusion is in some sense already contained in the assumptions. But many times you don’t know how to extract that information from the assumptions. You don’t notice that the assumptions contain it. And sometimes you need a very complicated mathematical or logical move in order to help.

[Speaker D] Right, but I’m asking specifically about the rhetorical side — because usually, parallel to “and Abraham went,” you bring the example of geometry in high school. And there it’s clear that theoretically we gained nothing, but it’s also completely clear that we still understood something. So here I’m wondering whether this isn’t more similar to “and Abraham went”?

[Rabbi Michael Abraham] I think it is. It is similar to “and Abraham went,” but the fact is that you see people still make mistakes. And everything I did here — my purpose here was not to prove to you that there is a God. I would really do that without any mathematics and without Bayes’ formula. My purpose here was to show why it is so important to define well the probabilistic question you’re dealing with. And the existence of God was just an example through which I demonstrated that. That’s all. You’re right that if I wanted to prove the existence of God, I wouldn’t go into this whole calculation.

[Speaker C] But doesn’t this again show how important our desire is in the way we look at the world? Because another person will look at the world and say — you can look and say what a complex and wondrous world, like Maimonides describes as the path to loving Him, right? What a marvelous world and so on. But you can also look at the world and say: what a crazy world, a world of suffering and destruction and cruelty. No, no, that’s not connected to the question of complexity.

[Rabbi Michael Abraham] No, and then the question is what the probability is…

[Speaker C] No. But that too is a kind of complexity if you see a kind of lawlessness, arbitrariness.

[Rabbi Michael Abraham] No. The world is complex even if there is a lot of suffering in it; that’s unrelated. Its entropy is low. It has nothing to do with the question of suffering. The question of suffering is another question, which really does come to challenge the existence of God — how can there be suffering here? A separate claim that has to be discussed separately. I’m talking about the question of complexity.

[Speaker E] What is entropy?

[Rabbi Michael Abraham] It’s a quantity in physics that measures the degree of order or complexity. A lot of people just think complexity is in the eye of the beholder. Among many atheists, when they argue against the physico-theological argument, they say: you think the world is complex because your mind is built in such a way that this kind of thing looks very ordered to you, very special. And that’s just because you’re built that way. So against that, I argue: no, that’s not true. There are objective measures of complexity and order. There are noises here… Whoever is speaking, please mute the microphone again afterward. Okay? What I want to claim is that there are objective measures of the degree of order and specialness of a system. In physics these measures are called entropy, and this has nothing at all to do with the eye of the beholder. Entropy calculations are objective scientific calculations. They have nothing at all to do with the eye of the beholder. The world is special regardless of what kind of creature is looking at this world. There is a calculation that shows that it is special. This is not something that depends on the eye of the beholder. That’s why I’m using the term entropy here. In any case…

[Speaker E] But doesn’t the very definition of “special” basically come from the fact that I need to compare it to other worlds?

[Rabbi Michael Abraham] Yes. So I ask: if you were to define worlds, how many worlds would you get at the level of order of our world? The answer is: a tiny number. That’s the more precise definition. Okay? You draw worlds at random however you like, any world at all. Okay? Now I ask: let’s arrange them according to an ordered hierarchy of order, the level of order in each one, which is basically the entropy measure. And now I ask: where is our world on that scale? The answer is: somewhere very high up. There are very few worlds at such a level of order, if I were freely drawing worlds at random.

[Speaker F] But how can you know that? I mean… There’s a calculation, it’s a calculation. You know only one world.

[Rabbi Michael Abraham] There are entropy calculations. That’s exactly the point.

[Speaker F] But we know only one world, don’t we?

[Rabbi Michael Abraham] So what? I can do the calculation for this world. I can calculate the entropy of this world even if I know only it, because I can imagine other worlds of all kinds and sorts and arrange them according to the level of complexity or specialness each world has, and ask myself: on that scale, where is our world? They don’t have to be real worlds; they can be imaginary worlds, it doesn’t matter, as long as I can describe them. It’s like thinking about four, five, or seventeen dimensions. Our world is only three-dimensional, but I can still define perfectly well worlds with two dimensions or with seventeen dimensions. There’s no problem at all. In any case, what I just wanted to show here is that these errors of mixing conditional probability with absolute probability, or mixing the probability of B given A with the probability of A given B, lead to many mistakes. Here are examples of that — we saw it in this calculation of the physico-theological argument. It’s an excellent example. And I’m telling you, this was with five professors at a conference on statistical inferences in physics. That was the topic of the conference. Five prominent professors were sitting there, one of them at least among the most prominent in the country. Okay? And they all apparently agreed — at least that’s how he described it — that this was the conclusion they reached. They all agreed on this complete nonsense, something for which I would give a high-school kid a failing grade if he wrote me an answer like that to such a question.

[Speaker C] So what’s the probability that five such professors at such a conference would make mistakes like that, assuming they’re intelligent?

[Rabbi Michael Abraham] Professors are not simple. The mistakes. Obviously they are intelligent, no less than I am — it’s not that I’m some great genius — I just think that at least I’m less biased. And the fact is that I sent him the argument and said this to him, and I got no reply. There is no reply; what he argued was simply mistaken. What happens is, when you look at believers and at proofs, seminars for bringing people to repentance and that sort of thing, it always arouses contempt — and truthfully, to a considerable extent, justifiably so. But that does not mean that everyone who brings proofs for the existence of God is talking nonsense. And their bias was this: that anyone who brings proofs for the existence of God is talking nonsense, and so immediately they throw out all kinds of arguments to explain why it’s nonsense, and you don’t really think seriously about what the other person said before you form your opinion. I’ve mentioned more than once the Talmud in Eruvin, where the Talmud says that the heavenly voice that emerged there said: why was Jewish law ruled in accordance with Beit Hillel? Because they were gentle and humble, and they would state the words of Beit Shammai before their own. Before they formed a position of their own, they listened to the arguments of Beit Shammai, weighed them, and only then formed their own position. Sometimes Beit Hillel even retracted and conceded to the words of Beit Shammai — this appears in the Talmud in several places. Meaning, Beit Hillel were people who seriously considered the position of those who disagreed with them before they formed their own position, and that is a guarantee of arriving at better conclusions in the end. Even though Beit Shammai were sharper, more acute, nevertheless Beit Hillel, because they were prepared to be balanced — meaning, to seriously weigh the arguments of the opposing side — even though they were less brilliant in terms of sheer intelligence, they reached more correct conclusions, and therefore Jewish law was ruled in accordance with them. And here you see exactly examples of that, and there are countless examples of it. Countless examples. I have a lot of arguments with atheists. Of course, you can always say that I too am biased; I’m also human. But my feeling is that sometimes you hear from very intelligent people arguments that are really foolish, and I can’t attribute that to their IQ — these are smart people. So my conclusion is that there is some sort of bias here, some kind of blind spot. They have a blindness toward the possibility that arguments leading to a different conclusion might actually hold water, might actually be correct. They are not willing even to consider that possibility. In the Talmud in Bava Kamma, in chapter two, there is the…

[Speaker C] What always bothered me about Beit Shammai is: why didn’t they — if they were so much sharper, and they also learned that Talmudic passage, then they could have thought of it themselves, that there’s room to put Beit Hillel first because they are humble and listen to the opposite view — so why didn’t they adopt that framework along with their wisdom and sharpness?

[Rabbi Michael Abraham] Because that’s exactly the point. Because we’re not talking about wisdom and sharpness; we’re talking about character traits. And very often, someone who is especially gifted has character traits that are probably less good, because he is so full of self-confidence that he isn’t willing to listen. Very often it comes in inverse proportion. So with all due respect to Beit Shammai, it’s uncomfortable to speak badly about them like this, but in my opinion that’s what the Talmud is saying.

[Speaker C] So in the end it comes out that what determines things is not sharpness and dialectics and rationality, but character traits and — what would you call it — emotions?

[Rabbi Michael Abraham] It’s clear that sharpness and intelligence help you reach correct conclusions, but there are things that can get in the way. In other words, good character traits plus sharpness—that’s the best combination. And there’s some kind of interplay between them: if you have good character traits, then you can be a little less sharp and still reach better results. If you’re a complete fool with good character traits, it could still be that you’ll be less correct. I don’t know how to formulate a general rule. There’s a passage in tractate Bava Kamma that I found—20a, in the topic of “this one benefits and that one does not lose.” We spoke about it in the past. The Talmud says this—and look, these really are very beautiful ideas, so I’ll allow myself to devote a few sentences to it. The Talmud says as follows: Rav Chisda said to Rami bar Chama, “You weren’t with us in the evening in the study area, and we raised some excellent points.” Right—you weren’t with us there in the evening, and you missed out; in the study hall there were wonderful things. He said: “What excellent points?” What wonderful things did you have there? He said to him: “If someone lives in another person’s courtyard without his knowledge, must he pay rent, or need he not pay?” That was the question asked in the study hall. And then it goes on to describe the discussion. It says: What are the circumstances? What case are we talking about? If it’s a courtyard not ordinarily rented out, and a man who does not ordinarily rent—then this one does not benefit and that one does not lose. Right? We’re talking about a courtyard that isn’t for rent, and a person who doesn’t need housing—he has housing of his own. Someone entered another person’s courtyard and lived there without permission. The question is whether he has to pay. Now, if the courtyard isn’t meant to be rented out, then the owner of the courtyard didn’t lose anything. I lived in his courtyard, but he wasn’t planning to rent it to someone else. So he didn’t lose. But I am someone who doesn’t need to rent—I don’t need housing, I have my own house—so I didn’t gain either. Therefore this is a case of “this one does not benefit and that one does not lose”: I didn’t benefit because I have housing, and he didn’t lose anything because it wasn’t for rent. But if it’s a courtyard that is ordinarily rented out, and a man who ordinarily rents—well that can’t be it either, because then this one benefits and that one loses. So if I benefited and he lost, obviously I have to pay. If I didn’t benefit and he didn’t lose, then obviously I don’t have to pay. So what case is it after all? The Talmud says: No, it’s needed for the case of a courtyard that is not ordinarily rented out, and a man who ordinarily rents. We’re talking about a courtyard that isn’t for rent—in other words, you didn’t lose anything, you’re not lacking—but I need housing, I went in there to live, so I gained, I benefited, while you did not lose. And about that the question was asked: does he have to pay or not? Right? What then? What—“What did I cause you to lose?” Can he say to him: look, what did I deprive you of? You haven’t lost anything, so why should I pay you? Or perhaps he can say to him: but you did benefit—after all, you benefited, so even if I didn’t lose, pay. Or in other words, he’s basically saying to him: is the obligation to pay determined by my benefit? Do I have to pay because I benefited? Or do I have to pay because you lost? What is the relevant factor for payment liability—my benefit or your loss? So if there’s both benefit and loss, obviously I have to pay according to both sides. If there’s neither benefit nor loss, obviously I don’t have to pay according to both sides. The practical difference will be in two cases: either I benefit and you do not lose, or you lose and I do not benefit—which only comes up in the medieval authorities (Rishonim); here it’s a dispute between Tosafot and the Rif. But in the Talmud it comes up when I benefit and you do not lose. So if loss is what causes the payment, then I don’t have to pay, because you didn’t lose. If benefit causes the payment, then I benefited, so I have to pay. That’s what the Talmud says. He said to him—so Rami bar Chama hears this enthusiastic description of the Talmud, of what happened in the study hall—and he says to him: what are you getting so excited about? It’s in the Mishnah—it’s an explicit Mishnah. The Talmud says: Which Mishnah? What Mishnah is that? He answered him—listen, there was such a beautiful analytical discussion in the study hall, we were all so excited—and he says: come on, it’s an explicit Mishnah, what are you all splitting hairs about here? He said to him: “When you serve me, then I’ll tell you.” I won’t tell you until you serve me. So he took his cloak and wrapped it around him—right, he dressed him with the cloak, served him. Then he granted his request and told him what the Mishnah was from which the question could be resolved. What Mishnah? “If it benefited, it pays for what it benefited.” Right? An animal that fell into a garden—okay, in the category of damage by eating or trampling—so if it benefited, say if this happened in the public domain, then it’s exempt from damages, but if it benefited—if it ate, for example—then it pays for the benefit it received. Rava said: how unhealthy and unsound is a man whose master helps him—what kind of foolish proof is he bringing from the Mishnah? Even though it isn’t similar to the Mishnah, he accepted it from him! There, it is “this one benefits and that one loses,” while here it is “this one benefits and that one does not lose.” In the Mishnah, what does it say? The animal falls into a garden and eats the fruits. In terms of loss and benefit, what do we have there? The animal benefited—it ate—and the owner of the fruits lost. And there, obviously it has to pay for the benefit, because there’s both benefit and loss. So why did you want to resolve from that Mishnah the question of “this one benefits and that one does not lose”? That’s a completely different question. And not only that, but after he brings him the Mishnah, the other one is silent—this is Rav Chisda, I think—yes, Rav Chisda is silent. As if he doesn’t say to him: listen, Rami bar Chama, what nonsense are you saying? It’s not similar at all. No—he was so captivated by him that he didn’t even notice what nonsense he was being fed. The Talmud asks: But Rami bar Chama—what did Rami bar Chama himself think when he brought this Mishnah? Didn’t he notice that it’s “this one benefits and that one loses”? They say: “Ordinary fruits left in the public domain are considered ownerless.” What does that mean? He put the fruits in the public domain, the animal fell on them or ate them, benefited from them—so on the face of it this is a case of “this one benefits and that one loses.” That was the question. The Talmud says no—this is a case of “this one benefits and that one does not lose.” Why? Because when he puts the fruits in the public domain, it’s as if he rendered them ownerless. And if he rendered them ownerless, then he didn’t lose the fruits. So the animal benefited and he did not lose. Now, that plainly cannot literally be what’s meant, because if that’s so then what’s the question? If you didn’t lose, why should I pay you? You made them ownerless. Why should I pay you for fruits you abandoned? Clearly the Talmud means to say this isn’t actual abandonment. The fruits were his; he didn’t really abandon them. But if he put them in the public domain, then he bears contributory blame. You put them there—you should have taken into account that animals could pass by there and eat the fruits. And because of that, it’s considered as though he did not lose. But the fruits are still his. Therefore there is room for discussion whether one has to pay him for the benefit the animal got, or does not have to pay him for the benefit the animal got. And that is the proof from the Mishnah. So yes, the proof from the Mishnah is in fact a good proof. Because what? The proof from the Mishnah really is speaking about a case like “this one benefits and that one does not lose,” and it says they must pay. From here there is proof that in a case of “this one benefits and that one does not lose,” one must pay. That is the flow of the Talmudic discussion.

Now there are several interesting points here. First, I also have a column about this on the site. I once brought this up in some panel at the National Library. First: why is he so excited about these “excellent points”? What is so special about this topic that he got so excited—what excellent things we had in our study hall? There I argued that in this topic something is formulated almost like an analytical inquiry of the later authorities (Acharonim). How would Rabbi Chaim write his little piece on this topic? He would say something like this: “And we must investigate whether the obligation to pay is due to the loss of the injured party, or due to the benefit of the damager.” What causes the payment obligation? The practical difference is in a case where there is loss but no benefit, or no loss but there is benefit. That’s the practical difference. And then you bring proof from the Mishnah, and so on. This is really a very Rabbi-Chaim-style move, right? Two sides, a conceptual inquiry, a practical difference that resolves the inquiry. This is very uncommon in the Talmud. The Talmud usually brings a case and compares it to another case. It doesn’t usually have this kind of inquiry that sets up two sides, understands practical differences, and resolves which of the two theoretical sides is correct. And that’s why he got excited. The excitement is about something we’re already so used to that we don’t get excited by it. But when the Talmud sees a move of Rabbi Chaim, or Rabbi Akiva Eiger, or whatever—a move characteristic of the later authorities—it gets very excited. It’s something brilliant, something analytically sophisticated, something the Talmud wasn’t used to in this form of thinking. That’s why he’s excited.

Now, he says to him: you can bring proof for this from a Mishnah—Rami bar Chama. So Rav Chisda says to him: which Mishnah? And he says: first serve me, serve me. Why? So Rabbi Shimon Shkop says in the introduction to Shaarei Yosher that he demanded service because he wanted to see whether Rav Chisda valued him. Meaning: if Rav Chisda values Rami bar Chama, then Rami bar Chama is willing to teach him. If you don’t value me, there’s no point in my teaching you. Why? Because if you hear something from me that you agree with, then you’ll agree—but you knew it already anyway, so you learned nothing from me. And if you hear from me something you don’t agree with, you’ll immediately throw it away and reject it. So practically speaking, you won’t be able to learn anything from me. After learning from me, you’ll remain with all the things you thought were true beforehand, and nothing will change for you—learning from me won’t help you if you don’t value me. By contrast, if you do value me, then even if you hear from me something that doesn’t seem reasonable to you, you’ll think twice, and maybe you’ll find that it is reasonable and learn something new. Maybe not, but maybe yes. And therefore, Rabbi Shimon Shkop says—he brings this Talmudic passage—and he says: whoever does not value me… because in Shaarei Yosher there are many strange things. And if, when you hear something there that doesn’t sound reasonable to you, you just throw it away immediately because it doesn’t make sense to you, then don’t open the book. You won’t learn anything. Only someone who values me, and when he hears something strange will think about it again and again, and only then form an opinion—like Beit Hillel with Beit Shammai—only such a person should study my book. That’s what he says there.

Now look how the passage continues. After he served him, he brings him the proof from the Mishnah. And then Rava, standing on the side, says: tell me, you two are a pair of fools. What, don’t you see that the Mishnah isn’t similar to our case? The Mishnah is “this one benefits and that one loses.” We’re talking about “this one benefits and that one does not lose.” Now both Rami bar Chama and Rav Chisda were hypnotized. They didn’t notice something that every first-grader would notice. And here’s the connection to us. How can that be? What, you don’t see that this is a case of “this one benefits and that one loses”? Any child learning this would immediately tell you: why are you bringing me proofs from the Mishnah? That’s “this one benefits and that one loses.” How did they not notice? Fine, so Rav Chisda was hypnotized by Rami bar Chama. But what was Rami bar Chama thinking? That’s what the Talmud asks. And then it says that “ordinary fruits in the public domain are considered ownerless.” Meaning: on the face of it, the whole thing sounds like complete nonsense. And Rava remains with the view that this is complete nonsense. Why? Because Rava doesn’t value Rami bar Chama. And when he hears from Rami bar Chama something that doesn’t sound reasonable to him, he says to him: you’re an idiot—sorry for the low language, but that’s basically what he’s saying. Forget it, you don’t interest me, you’re talking nonsense. But Rav Chisda—he served Rami bar Chama. He values him. So when he hears from Rami bar Chama something implausible, he thinks twice before rejecting it. And Rav Chisda thought about it and understood that although at first glance it sounds implausible—“ordinary fruits in the public domain are considered ownerless”—therefore it really is a case like “this one benefits and that one does not lose,” not like “this one benefits and that one loses.” But for that you have to think twice, because on the face of it, it sounds stupid. And that is done only by someone who serves his rabbi and understands or values his rabbi enough that even if he hears from him something implausible, he will think twice before forming an opinion about it. And it’s very יפה, because after this introduction of “serve me,” something really strange does indeed come. Without having served him, he would not have accepted it. And the proof is right there: Rava, standing on the side. Rav Chisda served him, so he accepted it. Rava did not serve Rami bar Chama, so he says: Rami bar Chama, you’re talking nonsense. Meaning, in the end we see—and that’s why I brought all this, it’s a bit long, but I think it’s beautiful, and it raises a lot of questions.

[Speaker C] Rabbi, Rabbi, that’s not an example. The Rabbi sometimes likes to say there’s no point in studying aggadic literature, no point in studying this stuff, because whatever you came in with is what you’ll come out with. If it doesn’t fit your morality, you won’t accept it—and if you won’t accept it… But when we approach the aggadot of the Talmud and study the Tannaim and Amoraim, and we respect them very, very, very deeply and value them, and also the heroes of the Hebrew Bible (Tanakh), then even when we face something that seems to us like nonsense or contradicts our morality…

[Rabbi Michael Abraham] I’ll answer. My remark is a factual remark. My remark is factual. In practice, all those who study aggadot and greatly, greatly value the Amoraim still don’t learn anything new there either. So you can’t buy that just on the level of my valuing the Amoraim.

[Speaker C] Does the Rabbi really think that if the Rabbi’s children had never learned any aggadot, didn’t know anything at all about the figures of Abraham, Isaac, Jacob, Joseph, David—all stories—and had learned only Jewish law, Jewish law from age three until today, they would be the same people they are today after they did learn those things? I have no idea, but that wouldn’t be a result of learning.

[Rabbi Michael Abraham] But again, we’re entering here into a topic that requires a long clarification. I’ve written quite a bit about it, so it’s better—I’d suggest—not to get into it now. That’s not learning. They heard the stories as children in kindergarten; yes, that built some kind of consciousness in them. That’s not what I call learning. Not that it isn’t Torah—it isn’t learning. It’s something else, it’s an influence of some other kind. Fine, but let’s leave that now. What I want to take from here is this: look how a smart person can arrive at a mistaken judgment because he is biased. Or alternatively, in the case of valuing one’s rabbi, this is a kind of bias—a corrective bias. Something sounds like nonsense to you, but you’re biased because you think this rabbi is a wise person, so you think about it twice, and suddenly you discover that it isn’t nonsense. And many times, valuation—this is what’s called the principle of charity—when you hear an argument from someone who disagrees with you, don’t seize on some point he missed or didn’t formulate precisely. Try… formulate his argument for him in the best possible way, and only then begin the discussion. Because catching him on some point he formulated carelessly—fine, you’ll come out the winner, but what did that help you? You’ll remain with the position you came to the discussion with. If you really want to learn, then you have to think carefully about the opposing position, and only then form an opinion about it. If you value the person who holds that position, then of course you’ll do that. If you think the person standing opposite you is an idiot, then you won’t do it. There really is no point in trying to erect some majestic position here if you have no appreciation for the one expressing that position. But in the end, with Beit Shammai and Beit Hillel, of course both sides were Torah scholars; no one there was an idiot. So Beit Shammai were sharper or more incisive, but precisely because of that Beit Hillel valued Beit Shammai, and therefore they weighed Beit Shammai’s doctrine carefully before formulating their own. And that caused it so that even though Beit Hillel were less sharp, they reached better, more correct conclusions.

And if I return to our issue—yes, this is a moral lesson, not related to statistics, but I think it’s very important, and that’s why I’ve taken up a bit of your time with it now. Many times, very sharp people, because they are unwilling to listen to the other side, reach incorrect conclusions: “From an over-sharp mouth comes error.” And sometimes it’s because of their sharpness. Their sharpness leads to error on two different planes. One plane: if you’re a sharp person, you can justify anything. You can always present an argument in favor of whatever conclusion you want. Someone who is sharp can prove whatever he wants. And on the other hand, the fact that you’re sharp also leads you to belittle your opponent and not weigh his words seriously, not to listen to his words. I have a question. There are two reasons why precisely the sharper people err more than those who are less sharp. Two reasons: first, contempt for the other and lack of listening; and second, sharpness enables me to prove anything. Therefore, as—who was it, not Oscar Wilde, also British, never mind—said: there are mistakes so great that only academics can produce them, things only academics are capable of saying. We see this with our own eyes, day by day. I mean, there are things so bizarre that come out of the mouths of smart people. Clearly this is some kind of bias, some kind of hubris, some kind of—I don’t know—you can attribute it to various things of that sort. And it’s because of the wisdom, not despite the wisdom. It’s because of the wisdom.

[Speaker D] I remember that Ilam Gross, at a certain point in his article, says the assumption that if God exists, then certainly there would be a world. And I wanted to ask: isn’t that assumption by itself enough to reach this mistaken conclusion? Meaning, even if the statistical calculation were completely correct, but it includes that assumption. No? Not enough?

[Rabbi Michael Abraham] No. Look at my column—no, it’s not enough. Okay. In any case, yes, so this is just an answer to the question of how smart people can reach such problematic conclusions. Okay, so I return to our topic. Basically what we discover here is that if I look at this in Bayesian terms, what this argument is actually doing is saying the following: given that my starting point is that the probability that there is a God is one-half, and the probability that there is no God is also one-half—the situation is evenly balanced, two equal possibilities—the physicotheological argument leads me to increase the weight of the probability that God does exist. Meaning, the probability that God exists, P of A, is one-half, but P of A given B is 0.99. In other words, the conditional probability is much stronger than the unconditional probability. Now why is that important? Because conditional probability is always probability on the basis of more information. We talked about this; I gave examples in the previous lesson. Suppose I throw a die. So I ask: what’s the probability it lands on five? A fair die: one-sixth. But if I know that the result will be odd, then the probability is one-third. Meaning, if I have more information about the possible outcomes, I can narrow the outcomes that can occur, and therefore the probability grows.

Now in our case, the discussion of whether or not there is a God is a discussion in the air. The atheists think there isn’t one, and I think there is. But it’s up in the air. Let’s see—but we do have data; it isn’t just floating in the air. There is a world here; a complex world exists here. What does that datum do? Which way does it move the needle? Does it increase the probability that there is a God, or not? That is basically the meaning of a physicotheological proof, and the answer is that it does increase it—significantly. If I start from the point of departure that it’s one-half, then once I also take into account the fact that there is a world, I suddenly get to 0.99—or I’m just throwing out a number—but much higher. Okay? So that is the meaning of a physicotheological proof. Therefore, when we look at probability, the physicotheological proof does not rest content with the probability that there is a God. That’s just begging the question. If you assume there isn’t, then there isn’t; if you assume there is, then there is. That’s a trivial case of assuming the conclusion. But the physicotheological probability argument says: forget what you think a priori; take more information into account. There is a world here, and the world is complex. Does that not change the probabilistic weights for you? The answer is that it does. And that is what this calculation does. So the meaning of the shift from absolute probability to conditional probability basically tells me that if I take into account more information or more data, the result—the probabilities of the result—can change. They can increase or decrease, doesn’t matter, but they can change. The probability that there is no God decreases; the probability that there is a God increases. As more information is added, it can change the probabilistic calculation, because the probabilistic calculation of someone who has a lot of information is not the same as that of someone who has no information or less information. Probability is a function of how much information I have. Because probability is always decision-making under conditions of uncertainty—but the question is how great my uncertainty is. If I have very little information, great uncertainty, then it’s like an a priori probability. If I have a lot of information, it may be very different from the a priori probability. And I need to do calculations of conditional probabilities, as we saw in examples in earlier lessons as well.

So basically I want perhaps to understand another example in the same context. When people bring the physicotheological proof, let’s focus for a moment on the origin of life. The claim is that a living being is a very special being. And again, low entropy—this is objectively special. It’s not in the eye of the beholder. So this is a very special being, and therefore it is improbable that it came into being without a guiding hand. Therefore there is a God—this is one formulation of the physicotheological proof. You could call it a biologico-theological proof. So that’s the formulation. Now this is really the role that evolution plays in this discussion. Why? Because evolution is basically trying to offer me an alternative mechanism, without assuming the existence of God, and still explain how in a spontaneous way a sophisticated being, a special being, can arise. How? Through evolutionary processes. Okay—natural selection and genetics and the formation of mutations; mutations arise, natural selection preserves the more survivable or fitter mutations, and genetics passes them on to the next generations. That’s the genetic path, the evolutionary path. And this basically says that we have a completely natural explanation for the origin of life. Therefore the assumption that a complex thing cannot arise spontaneously without the possibility of a guiding hand—that assumption is false. That assumption has fallen. And therefore the physicotheological proof has fallen. That is essentially the whole polemic around evolution.

Now I’ve also spoken about this more than once, and written about it. Where’s the mistake here? The mistake is that you’re looking at the problem from within the laws. Given the laws of nature, I can show you that life can arise without anyone being involved. The big question, of course, is who created these laws of nature within which life can arise spontaneously? If the laws of nature were different, then life would not arise spontaneously. Even the tiniest change whatsoever would destroy the possibility of biology existing at all—chemistry, biology, everything needed on the way to living organisms. Therefore the question is not whether you have a scientific explanation for the origin of life. That’s “God of the gaps.” Right? Meaning: if you don’t have an explanation, that means there is God. That’s the God of the gaps, yes? The moment there’s a gap in scientific knowledge, that means there is God. “The believer’s celebrations are always faithfully held whenever the weather forecaster was wrong”—that’s always the example standing before me. Whenever the weather forecaster is wrong, they celebrate. Yated Ne’eman declares a holiday. Why? Because from their point of view, if science is right then there is no God; if science is wrong then there is God. That is exactly an expression of the God of the gaps—proving the existence of God from our gaps or scientific misunderstandings. And on that many atheists rightly claim that one should not bring proofs for the existence of God from gaps in scientific knowledge. Gaps in scientific knowledge get closed through scientific research. Five hundred years ago there was much more God, because we had many more gaps in scientific knowledge. That has closed. So the gaps that exist today may also close in the future. You can’t build any conclusion on the existence of those gaps. Maybe it’s simply because we haven’t finished investigating. We’ll investigate more, and we’ll know that too. Therefore, God of the gaps is not a valid proof for the existence of God.

But when I speak about proof from the laws—what I call it—I mean that I prove the existence of God not from the origin of life, but from the origin of the laws within which life can arise spontaneously. And precisely because the system of laws is like this and not even slightly different. If it were even a tiny bit different, this could not happen. Now here you can no longer talk to me about evolution; there is no evolution of the coming-into-being of systems of laws. So you’ll say: fine, then they’ll find some other scientific field that explains how the laws came into existence. That is still God of the gaps. You are basically telling me: I don’t understand something scientifically, therefore there is a God. That’s God of the gaps. I say no. Why no? Because even if they find a scientific explanation for the laws that govern the world, that scientific explanation itself will also rely on some laws—meta-laws—that govern the formation of laws. Then I will ask: who created the meta-laws? What will you tell me—turtles all the way down? In other words, at some point there is some initial command, yes, which is the basic law—the unified field theory, as Einstein called it, searched for desperately and didn’t find. And to this day there is hope of finding it. But even that unified field theory will be one law from which everything is derived. And the question will still remain: who created that law? And this cannot be closed by scientific research, because scientific research at most discovers more scientific laws. But here you need some explanation without scientific laws. There is no scientific explanation without scientific laws. Therefore here this is an essential claim; it is not God of the gaps. I claim that the existence of the laws is the proof for the existence of God, not the origin of life. The origin of life, given that these are the laws—fine, of course. But why these laws?

Now in the last formulation I gave, you understand that this is exactly the difference between probability and conditional probability. The original creationists bring a proof in terms of conditional probability, a proof from within the laws. They say: how can life arise without a guiding hand? There’s no chance life could arise without a guiding hand. The answer is: not true. Evolution shows us that there is such a possibility. There is a possibility for life to arise without a guiding hand, through the laws—through behavior according to these laws, life will eventually arise. But that process is a conditional process. Given that these are the laws, what is the probability that life will arise? The answer is one. And now I ask: what is the probability that life will arise unconditionally—not given that these are the laws? What is the probability that life will arise? Or in other words, what is the probability that these will be the laws? If this is P of A given B, then you have to multiply it by P of B. Meaning: P of A given B is one. But what about P of B? B is that these are the laws, and A is that life arises. Given that these are the laws, then life arises—the conditional probability is one. But what is the probability that these would be the laws? Why assume that these would be the laws? What is the probability they came into being just like that? Here the probability is very small, and that is what proves the existence of God—not the conditional probability. Precisely the absolute probability proves the existence of God. So here the mistake is the opposite mistake. Instead of looking at the absolute probability, you look at the conditional probability. The conditional probability is high, that’s true, but the a priori probability is tiny. So again, moving from conditional probability to unconditional probability—given that these are the laws, which is the extra information I have—what is the probability that life will arise? The answer is one, or almost one. Okay? But that is conditional probability. I’m asking: what is the probability that life will arise, period? Or what is the probability that laws will arise that allow the spontaneous emergence of life? That probability is very small, and on this point it is not God of the gaps. Here I really can infer the conclusion that there is a God, because without God such a thing could not have happened.

[Speaker C] Another claim of yours—the complexity drops out of the picture; right now we’re talking about the most basic fundamental law.

[Rabbi Michael Abraham] No, he’s answering—the complexity does not drop out of the picture. Suppose the law…

[Speaker C] No, no, I’m talking about the law itself—what does it contain?

[Rabbi Michael Abraham] What? No, that’s the complexity of the law. The complexity of the law is that this law produces very, very complex beings. If this simple law were a linear law, y = ax + b, you have two parameters a and b—that’s the unified field law. But a has to be exactly pi over four. If you deviate a tiny bit to the right or a tiny bit to the left, nothing will come into being. That is a special law, even though its formula is very simple. It is a very special law. And the question remains the same question: how did a come out exactly pi over four? The complexity remains; it doesn’t matter how much you simplify the system of laws.

[Speaker C] Its outputs would be complex. I don’t know—there are infinitely many worlds, there are infinitely many worlds, infinite… No, I don’t mean—I don’t understand—some event happened and some…

[Rabbi Michael Abraham] That’s a different argument. I’m willing to argue with you about that too—I’ve written about it as well. But that’s a different argument. I’m trying to illustrate the difference…

[Speaker C] No, how can one determine the…

[Rabbi Michael Abraham] The statistics?

[Speaker C] I’m asking the Rabbi: what is the most fundamental law of the universe? Suppose the Rabbi defines it for me. It’s terribly, terribly simple. I don’t know—let’s just describe it schematically: two hydrogen molecules, I don’t know, connect. I’m just saying some nonsense. The simplest thing in the world, and that causes the Big Bang and then it rolls forward. Now, there’s no—this very fact that two hydrogen molecules connected is, let’s say, very simple to explain. Now, the fact that there is… no, it’s not simple.

[Rabbi Michael Abraham] No, no, no, no, no. I’m stopping you there. What does “simple to explain” mean? There is no explaining it. That is the law; it explains other things. It itself cannot be explained. I’m not explaining—what is the explanation for a law?

[Speaker C] The law itself is simple; its consequences are very complex. It led to the Big Bang, which rolled…

[Rabbi Michael Abraham] Exactly. But that law is a very special law. If you just drew a random law, it would not have complex consequences. So that law is a very special law, and it requires an explanation.

[Speaker C] But how can one determine the probability that such a thing would happen?

[Rabbi Michael Abraham] Well, by… think about it: if you draw laws completely at random, how many of the systems of laws you draw will produce a world with this level of complexity? The answer is: almost none. That is the specialness of the system; that is what defines the specialness of the system.

[Speaker C] Wait, aren’t there infinitely many other laws that would create other worlds?

[Rabbi Michael Abraham] No. And if there are infinitely many, it is still an infinity that is very small compared to that infinity. Think of the natural numbers versus the real numbers. Still probability zero. It doesn’t matter that there are infinitely many; that isn’t important. There are infinitely many. Meaning, if you increase all the physical constants in the same proportion—that is, keep the ratios between them—every such system of constants would create a complex world like ours. Human beings would just be smaller, bigger, or fatter. But it would still create the same complexity. There are infinitely many laws that create that, but that infinity of laws is such a tiny infinity compared to the totality of all possible laws that it is still negligible. The probability is zero. What? Think of drawing a real number—what is the probability it comes out an integer? There are infinitely many integers. Zero. Do you understand? It doesn’t matter that there are infinitely many integers.

Anyway, once again, I’m bringing here an example from another angle of the need to be careful not to confuse conditional probability with absolute probability. In this case it’s the opposite confusion. Meaning, the atheist uses conditional probability and the believer uses absolute probability. In the case of the physicotheological proof, it was the believer who used conditional probability. Okay? But still, these confusions are confusions that show up in a great many arguments. Even in arguments where people do calculations, and with numbers—as the advertisements say—you can’t argue. Well, actually you can argue with numbers even more than with logical arguments. Because behind the numbers there are always all kinds of assumptions. And for some reason, when you focus on the numbers it blinds people; they think there’s an argument here that can’t be disputed.

I’ll perhaps bring another example that illustrates this point. We’ve talked about it in the past as well. We know there is a rule that “the burden of proof is on the one who seeks to take property from another.” If someone sues me over some item of property that is in my possession, then he is the one who needs to bring evidence in order to take it from me. If he brings no proof, it stays with me. What is the logic behind this rule? There are later authorities (Acharonim), and it’s also commonly thought in the world, that the logic is possession—the presumption that what is under a person’s control is his. There is such a presumption in the Talmud: what is under a person’s control is his. Usually, if it is with me, it is probably mine. So if now you sue me and I say you’re wrong, the burden of proof is on you. Why? Because in the ordinary state of affairs, if it is with me, it is probably mine. That is the common explanation. Except that it is not the correct explanation, and it is incorrect for the very same reason we are talking about here: because this involves conditional probability and not absolute probability.

What do I mean? Think, for example, of a situation in which we go through all the objects in the world, in all the houses of all people, and we record for each one whether it is with its owner or not with its owner. We will get an overwhelming majority of objects that are with their owners. Right? That is obvious. Meaning, if an object is found in a certain place, usually it is with its owner. In other words, most objects are with their owners. Okay. But now I ask another question. If someone comes and sues me over, say, this phone here, okay, which is in my possession, and he claims that I stole it from him and I claim nothing of the sort—can one say that this phone is probably mine because what is in my possession is usually mine? The answer is no—or not necessarily. Why? Because the statistics I described earlier were done over all objects in the world. If you go over all the objects in the world, in most cases the object is with its owner. Okay? But if you focus on the subset of objects over which there is a legal dispute—let’s look only at that subset—then in that subset there is no reason to assume that plaintiffs are bigger liars than possessors, right? The plaintiff has a presumption of integrity, and the possessor has a presumption of integrity. There is no reason to assume the plaintiff is lying and the possessor is not. The conclusion is that if you focus on the group of objects over which a legal dispute is being waged, the probability that it is mine or yours is fifty-fifty. Even though, over all the objects in the world, clearly there is an overwhelming majority of objects that are with their owners. So what does that mean? It means that if I look at the absolute probability and say: given an object, what is the probability that it is with its owner—what is the probability that the one holding it is its owner? The answer is ninety-five percent. But now I look at a conditional probability: given that there is a dispute over this object—and there are only very few such objects in the world, objects over which there is legal dispute—given that this is the case, what is the probability that the one holding the object is the owner? Fifty percent. That is the difference between absolute probability and conditional probability. As I said, conditional probability is always a probability that focuses on a subspace, yes, on part of my event space. I’m not looking at all the objects in the world, but only the disputed objects. I’m not looking at all worlds, but only the complex worlds. I’m not looking at all systems of laws, but only at the special legal system that is here. And now I try to infer conclusions. So conditional probability basically means narrowing the gaze to a subgroup or subpart of my event space.

[Speaker D] Can’t one treat this conditional probability as the product of the honesty or credibility of the two sides, which is, say, one-half, together with the absolute probability—that ninety-five percent really are under their owners’ control—and then it would still come out…? Why not?

[Rabbi Michael Abraham] What? Of course not. What do you mean, product?

[Speaker D] Because the general argument is also relevant, no? The general argument suddenly isn’t relevant?

[Rabbi Michael Abraham] It’s not relevant at all. Why not? There is no product here. A product applies when you need both things to occur, and each one separately has a certain probability, and they are independent—then you can multiply the probabilities. But here there is dependence. If I am lying, that means the object is not mine. The question whether I am lying or not and the question whether the object is with me or not are not two independent questions. If I’m lying, that means the object is not mine. You can’t multiply probabilities when the variables are dependent. What you would have to multiply now is probabilities in the following way: you would have to say what is the probability that this object is mine, times the probability that I am not lying, times the probability that I am not lying given that it is with me—like Bayes’ formula. Do you understand? You can’t multiply the probability that the object is with its owner, the general probability, by the general probability that a person lies. You need to multiply an absolute probability by a probability…

[Speaker C] I don’t understand, but that’s just begging the question again. The object belongs to this category of objects that are in legal dispute—that’s what we’re trying to determine. Obviously that’s influenced by credibility. Suppose we’re in some country—not Israel, some other country—where there are no liars. They have some illness like that, they don’t lie; some virus infected everyone, they don’t lie. It’s very rare that someone—some mutation, some oddity—actually lies. Then we see—right, not exactly, but to say that they lie, there’s no such thing. It’s very rare, really an unusual phenomenon. So then I really would use the general probability. So we do see that we look at the general population and say: most people… If we’re in Sodom—no—but there you’d be right—

[Rabbi Michael Abraham] But there indeed the relevant probability would be the general probability, that’s obvious. But we don’t live in such a world.

[Speaker D] Why? But on both sides they don’t lie, but—

[Speaker C] We are influenced by that, we are influenced by what happens in the general population. If we’re in Sodom, where everyone steals from everyone, then we aren’t influenced by anything.

[Rabbi Michael Abraham] Our world is a world in which people do lie. Our world is a world where, when two people are arguing, a very reasonable assumption is that one of them is lying, not that one of them is mistaken.

[Speaker C] No, okay, I said that was just an example I brought.

[Rabbi Michael Abraham] And then we can relate to the absolute probability.

[Speaker C] But there’s no difference, for example, if we’re discussing it—there’s a presumption—if you come to Sodom, where everyone steals from everyone systematically and that’s obvious, and you come to Israel, where that’s not the case. Does that presumption exist? Right, and here it would. In Israel it would, because people steal less, the general population steals less.

[Rabbi Michael Abraham] Not only because of that. That presumption exists here because there are legal reasons for that presumption, not probabilistic reasons. The probabilistic reasons don’t exist. There is no probabilistic consideration in favor of the current possessor. There is a legal consideration. A sensible legal order says that in order for the religious court to take action, you have to persuade it; otherwise it doesn’t intervene, and the object will therefore remain with the person holding it. But that’s a legal consideration, not a probabilistic one. Probabilistically, the chance is fifty-fifty that it’s yours.

[Speaker C] But if, Rabbi, we were really betting on it, we’d say it can be clarified, we’d be able to determine it with certainty in the end—the Rabbi wouldn’t, if he were a person who came to some organized country, I don’t know, to Sweden, to Norway, let’s say everyone there is honest, and I make a bet with the Rabbi, a wager, then—

[Rabbi Michael Abraham] The Rabbi would say—

[Speaker C] —that it belongs to the possessor?

[Rabbi Michael Abraham] Obviously, but—

[Speaker C] That’s a different country.

[Rabbi Michael Abraham] We don’t live in that reality. And Hazal didn’t live in that reality either. It’s not a matter of the decline of the generations.

[Speaker D] But is there no possibility of a situation where in fact neither side is lying, but one is mistaken?

[Rabbi Michael Abraham] In cases of mistaken perception, yes.

[Speaker D] I mean also in a reality where there is an equal presumption of reliability for both sides, where each of them lies half the time and tells the truth half the time—on the possibility that they’re mistaken, don’t we still have to take the overall absolute probability into account?

[Rabbi Michael Abraham] Of course we do, and that’s what I said earlier. In a world where no one lies, and if there’s a dispute then apparently one of them is mistaken, not lying, then I would use the general probability there, without a doubt.

[Speaker D] But I’m asking: in a world where people do lie, is there still no chance that here no one lied, and we still need to take into account the possibility that someone is mistaken?

[Rabbi Michael Abraham] And in fact, in situations where the possibility of mistaken perception arises, the law really does change. For example, migo does not apply against mistaken perception. Because migo proves that you’re not lying, but if my concern is that you’re mistaken, then what does it help me that you have migo? Usually the assumption is that when there’s a dispute, one side is lying. If there’s a possibility that one side is only imagining things, as in identifying the dead, yes, in permitting agunot and so on, then there is mistaken perception, and the rules really are different. Okay, so I’ll stop here. If there are questions or comments? Rabbi, Rabbi, maybe…

[Speaker C] The Rabbi said that he doesn’t like talking about aggadic literature and that we don’t derive things from aggadic literature and so on and so on, but when the Rabbi does end up talking about aggadic literature, somehow it comes out extremely well, like today, in today’s class. Maybe the Rabbi will consider in the future doing some kind of series, I don’t know…

[Rabbi Michael Abraham] But aggadic literature here is the narrative framework for Jewish law; this is a halakhic discussion. One benefits and the other doesn’t lose.

[Speaker C] No, but I mean drawing philosophical values דווקא from aggadic literature, like he does at Bar-Ilan on topics in the Talmud. Just a suggestion for the future, because it came out very successfully; this aggadic passage seems very fundamental in this explanation.

[Rabbi Michael Abraham] Yes, well, maybe. But you understand that this still fits my rules, because it leads to a conclusion that I already identify with in advance. It’s not that I disagreed, but because it says so in the Talmud I changed my mind. The Talmud served me as a nice illustration of a principle that was actually clear to me even beforehand.

[Speaker C] Right, but if the Rabbi had told me—or us, I don’t know, at least me—the lesson beforehand, just some seemingly basic lesson like he said, as opposed to when he described it… it hit me much more strongly. Very differently, completely—it changes things, it’s tremendously important in the end. That’s also the lesson of aggadic literature, that kind of human impact.

[Rabbi Michael Abraham] Yes. Okay. It has rhetorical value, I agree. Okay then, Sabbath peace, and may we hear good news.

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