Q&A: A Fortiori Inference
A Fortiori Inference
Question
Following your lecture today.
Within the Talmudic passage about not deriving something learned from something already learned in the realm of sacrificial matters (Zevachim 50b), there is a logical-philosophical discussion of the principle of a fortiori inference. The passage implies that a fortiori inference is not a transitive relation. If it were transitive, then if a is more stringent than b, and b is more stringent than c, then necessarily a is more stringent than c, and one could derive directly by a fortiori reasoning from c to a. But the very fact that the Talmud there asks, “Something learned by a fortiori inference—can it itself be learned by a fortiori inference?” shows that one cannot derive the final case directly from the first, but rather that two entirely separate derivations are needed.
My conclusion from this is that relations of stringency do not necessarily lie on a single axis, and therefore the fact that a is more stringent than b cannot say anything about its relation to c. From here comes the idea that stringency can lead to leniency. And it seems to me that this connects to what you argued today.
Have a good week.
Answer
Have a good week.
Indeed, this is a very interesting passage in this context. First, the stringency of a over b could be in terms of “charge” X, while the stringency of b over c could be because of charge Y. So there is clearly no a priori reason to assume transitivity.
The problem is that if there were a logical explanation of this sort, we would have to establish a similar rule throughout the Talmud and not only in sacrificial matters. So it seems that there is a principle here specific to sacrificial law. And perhaps in sacrificial matters the assumption is that the axes of stringency are not clear to us (because the topic is not connected to our everyday life, unlike tort law for example), and therefore specifically there there is no transitivity.
Beyond that, there is a rule that one does not derive an a fortiori inference from a law given to Moses at Sinai. Simply speaking, that is because a fortiori inference is one of the interpretive principles, and those principles deal with Scripture (you do not make a verbal analogy or a general-and-particular inference within the Talmud or in Rashba). Once you have learned some law by a fortiori inference from the verse, the result itself is no longer a verse. Therefore you cannot apply the principle of a fortiori inference to it.
There in the passage they discuss combinations of several different interpretive principles layered on top of one another, and it seems that this is not a statement specific to a fortiori inference. Still, there are some combinations that are in fact legitimate, and further analysis is needed as to what exactly the criterion is.