The only difference between the existence of free will and the existence of ghosts is the effect on the ego.
There are people whose ego would be hurt if they knew they had no free will. With ghosts, that issue doesn’t exist.

In short, “free will” still exists in discourse thanks to the ego.

Just to expand on what Doron said: the absence of free will actually cancels not only the truth-value of claims, but their meaning altogether. If every claim is true (and to the same extent also not true), then no claim points to any external reality, or in fact to any reality at all. And therefore it doesn’t point to anything, and so it doesn’t say anything either.

And to explain further why lack of choice means there is no truth, one has to add that the whole concept of truth is actually built on a picture formed in our consciousness, and forming it involves, among other things, a decision to trust the data of our senses and our intellect (and not just the decision; there also has to be additional external feedback, and accepting that too again involves trusting our senses).
That decision involves free choice. Without the decision, we don’t really have such a conscious picture. So there is no consciousness at all. There is only stimulus and response, like with animals. With animals there is no truth (and no experience of truth either), because they have no consciousness. There is no such thing as a lying dog. And there is also no difference between a mad dog and a dog that isn’t mad (the difference exists only from our perspective, not from theirs). If a dog “decided” that you threaten it (even if you don’t), then from its point of view that is the truth—although it isn’t. As I said, for it there is no truth. It’s a robot. It is programmed to decide that you are a threat according to various parameters. And a mad dog is programmed to decide according to different parameters. But biologically there is no difference between them.

There are many animals that are very aggressive and hostile toward humans for no “real” reason. Hippos, for example, kill many Africans every year because they are extremely territorial, and if you accidentally enter their territory (without even knowing it is theirs or that they are sensitive about it), they will attack you anyway, even though you had no evil intention at all. And you can’t say they attack by mistake. With them there is no mistake. Only stimulus-processing-response. No judgment or discretion (free will) is involved.

Doron and Immanuel, the main point here (the epistemological problem for someone who holds determinism) is a well-known and developed argument of Rabbi Michi’s. But you can’t present it this simply.
You have to start with the basic and simple observation that a “decision” made by free choice cannot increase certainty about anything. If the picture in consciousness reflects reality, then it reflects reality, and if not, not—and it makes no difference whether the observer decides to believe the picture in his consciousness, or decides not to believe it, or whether the decision to believe is forced on him and he only imagines that he decided.
And afterward, in order to establish Rabbi Michi’s claim, you need all sorts of twists and refinements.

Tirgitz, I didn’t understand your reservation. If you can, please explain it again more simply. In general, Immanuel sharpened my point, and I completely agree with his claim that not only truth is harmed by the rigid deterministic position being presented, but meaning as well.

(I don’t have the strength right now to get into the discussion itself and all its twists. I only came to say that the claim that there is an epistemological problem in assuming determinism is a novel and subtle one.)
Usually, what is forced upon consciousness is considered more reliable—I believe more in the fact that there is a table next to me than in the idea that objects fall to the floor. Does my belief in sensory perceptions (or intellectual perceptions, or any factual opinion) depend on my having “chosen” to believe them (that is, I chose to accept various assumptions so that there would also be a “justification” for my accepting that perception), rather than everything being forced on me? In your words and in Immanuel’s I didn’t see anything connecting those two. And if in your opinion the argument as you presented it is complete and sufficient, then I’m not arguing.

I’m not sure I understand what you mean, but it seems to me that you’re going down into nuances that aren’t relevant to the basic claim from which our discussion grew. There may be information forced upon us. For example, the quality of redness that we encounter when we see a strawberry. That is the empirical domain, and here there may be a “deterministic” component for creatures with an eye and brain structure like ours.
By contrast, the sweeping claim, “There is no free will,” carries metaphysical, epistemological, psychological, and other status, and it is certainly not necessary. One can hold other claims, and even argue about them and change one’s mind. But when someone like Sam Harris categorically determines that there is no free will, he is pretending to grant precisely those sweeping claims a necessary status that turns them, paradoxically, into claims without truth-value and even without meaning.

There is no coercion here on consciousness. There is simply a stronger sense of self-evidence than usual, because it is more tangible and less abstract, and therefore easier to see. So it is also more reliable. By the way, the meaning of the word “reliable” is “trustworthy.” And that’s exactly the point: something one can place trust in. And placing trust is a matter of choice. “One can believe it” means that the consequences of trusting it were good and not bad. Note that perception itself—any perception, even intellectual perception—is not a matter of choice, but trusting it is.

You can choose not to believe the data of the senses. True, that has consequences (being hospitalized in a psychiatric ward, or crashing after falling off a building), but one can choose to go mad. In general, in the progressive world people deny reality and also deny the consequences of denying it. And that’s about things that once were clear to every reasonable person (and therefore progressives are not reasonable people, etc.).

What you are talking about with justifications is simply what is called “knowledge.” Knowledge is belief in a solid state of aggregation—strong belief. That is, belief that has brought in its wake a critical mass of good consequences for the believer. But really, knowledge too is a kind of belief. The law of gravity can never be proven. It’s just that our trust in it keeps getting stronger through experience. So we say that we know it is true.

Maybe I misunderstood your argument (I interpreted it in a way I could understand, and apparently that’s not what you meant), and the whole conversation got blurred. I don’t think that choice or no choice changes anything (with practical consequences, not existential depression), but we’ll leave that for another time.

Tirgitz, could you write out the argument in more detail? I never understood Rabbi Michi’s argument on this issue.
At most, even if there’s an error, you too will probably err…
The senses do not faithfully reflect reality, Descartes’ demon, etc.

My strength has failed me and my bones are weak, etc. Maybe try In the Sciences of Freedom (or on the site).