Free will isn't an illusion so much as a misleading oversimplification of a complex concept.
The traditional philosophical notion of free will assumes a kind of perfectly rational Platonic ideal of a thinking human who carefully weighs all future options before acting.
This is clearly nonsense, and should have been called out as nonsense much earlier in history.
In reality free will is a mash-up of all kinds of influences - rationality, misguided belief, instinct, genetics influencing brain structure and hormonal balance, culture, previous experience - in varying proportions.
They add up to a kind of meta-freedom - not necessarily rational, but not particularly easy to predict or control with any precision.
Your sense of self isn't aware of these influences, but that won't stop you acting with some form of independent agency - and that's still true even if there's a gap between your conscious model of your motivations, and the soup of real motivations that drives you.
> that's still true even if there's a gap between your conscious model of your motivations, and the soup of real motivations that drives you.
I would say it's true because there is a gap, not "even if".
What decisions do you make differently with your knowledge that free will is an illusion? What choices do you make differently?
(fwiw, I agree with you; I just think it doesn't particularly matter now.)
Interestingly, my belief in the illusory nature of free will has had a huge impact on my life. I'm a much more laid-back person than I used to be. I don't stress out so much over making mistakes. It has also helped me in a lot of practical aspects of my life. For example, it has helped me lose weight. I think about my desire to eat as my brain playing a sort of a trick on me, and that makes it easier for me to "decide" not to give in to the craving. I treat the part of me that wants to eat the cookie as a separate entity from "me" that just happens to reside in the same brain, and I interact with it through internal dialogs like I would a small child. It sounds weird, but it works, at least for me. I'm almost down to the same weight I was in college (and I'm 54).
Horizontal gene transfer? A literal virus that changes who you are. It's interesting to think that by going paleo or vegan you can perhaps become another "person"...
Not really, few physicists have tried to explain consciousness - Roger Penrose being a notable exception - and no physicist has ever sufficiently explained how artifacts like the complete works of Shakespeare come about. They seem to have been invented by Shakespeare but if Shakespeare had no free will to invent them, then were did they come from? While we're at it, where does the continuum and the mathematical structures between real numbers come from? Are real numbers even physically possible? I've read a paper once that argued that they cannot be physically realized, because that would violate the laws of thermodynamics (and a few others, too). What about the rest of mathematics like perfect squares or functions that cannot be computed? Are these illusions?
In a nutshell, there is a whole lot that physics cannot explain, including all of human culture. That's the gist of Popper's three worlds argument. Physicists surely claim that the physical world is closed, but they haven't provided any arguments that go much beyond "human culture is super complex but we believe we could in principle explain it somehow with our theories".
Now Popper argued for some not too plausible dualism, but the central negative part of his argument still stands.
As for explanations, I agree that not many good ones are on the table and maybe the Philosophy of Mind confuses more than it clarifies. My personal favorite speculative theory is a rare form of computationalism, namely the position that some computations might have consciousness as an emergent property when they run on a suitable physical device, and that in theory we could even be able to determine which class of computations these are by mere analytical insight, provided we have the proper conceptual tools. Computationalism is not very popular in philosophy, though.
Who (or more precisely what component of "us") is it exactly is it that has free will? The ethereal eternal soul (which is that anything but an imagined property of conscious beings)? The meat abacus in our heads? the nerves in our arms?
I'm pretty sure that I'm in a better position to know what I actually believe than you are, and I'm telling you, I really do believe this. There are only three possibilities: either free will is an illusion, or dualism is true, or consciousness is the result of unknown new physics. The first is by far the most likely from a scientific point of view, and the evidence for it is actually pretty overwhelming.
But just because it's an illusion doesn't mean that you can't or shouldn't live your life as if it were real. It's a very compelling illusion as long as you don't know how the trick is done, and so far, we don't.