This topic has been buzzing around my mind for a while, so I figure it's time to externalize it. "Free will is an illusion" is a meme that I've seen quite a lot on this site especially. I don't think most people who repeat it have thought much about it.
Yeah, materialism (which I hear is popular around here) suggests a mechanistic universe, one without true randomness, defined solely by predictable input and output. That contradicts our intuition about independent free will, which seems unpredictable (or at least not fully predictable) when we experience it. I don't think a fully mechanistic universe is incompatible with free will, though - in fact, I think that any coherent definition of free will must necessarily exist even under a materialist lens. Those of you who are (like me) pop-philosophy dilettantes probably know that this position is called "compatibilism".
Obviously, though, people disagree. I want to know why. If you don't believe that free will exists, under what circumstances do you think it would exist? What do you think would change if it did exist according to your definition?
I think my own neurodevelopmental disorders definitely led me to intuitively rejecting free will. When you have ADHD and BPD and you can't fucking clean up your house over and over despite wanting to because there ain't enough molecule in your brain, you start to understand how that applies across the board. The well functioning brain doesn't have to consider that the rewards it receives determines the actions it engages in, and that the response to the reward is entirely beyond them, for instance.
If you're anxious and how you act, who you are, what you've done has been fundamentally conditioned by overactivation of the hypothalamus-pituitary-adrenal axis, the friends you have and the environment you find yourself in and the jobs you can perform, good luck finding the freedom in that. The obverse is still true, an HPA system that works well is still determining these things, just positively and without friction.