Whether or not the universe is deterministic we don't have free will. Because free will is a self-contradictory concept. Free will is a square circle, a squircle. Here I’ll try to explain why free will illusionism is the correct stance.
What is free will?
Based on how I hear people use the term most often, I consider free will to be a quality an agent can possess such that the agent could have deliberately decided differently, for any actual decision they made. My compaint with compatibilism is that it doesn't speak to this sense of the term free will, which I believe is the most relevant because of how widespread it is.
By could have decided differently, I mean if the state of the universe was somehow rewound to just before I chose to drink that last beer, everything identical to the first time around, free will would make it possible for me to deliberately chose not to drink the beer instead.
Why is the deliberately part important in this definition? If we imagine a system in a person's head that resolved decisions solely on the basis of some kind of quantum randomness, there’s a sense in which that agent could have chosen differently in an identical universe, but they would not seem to be the authors of these differences. The differences wouldn’t be the product of deliberate thought, and so not the product of will. And since free will is a kind of will, we have to be able to describe its decisions as deliberate.
Could have deliberately decided differently
The Deliberately refers to the will part of free will. This is where the idea links to the continuity of the self, and an agent’s sense of owning the decision.
The Differently invokes the more mysterious free quality of free will, the idea that there’s some part of decision making that’s unconstrained by the prior state of the universe.
Will is prior brain state
A decision is mine, it’s the product of my will, to the extent that the prior state of my brain causes it. That state includes my preferences, habits of thought, memories, goals and everything else that makes me me.
To the extent that a decision is the product of anything else (which it would need to be, to be free in the relevant sense), it’s not recognisable as mine, not recognisable as a product of my will.
Will can’t be free, and free can’t be will.
How does free will reach its decisions?
For any decision there are three possibilities:
- The decision is fully caused by the prior state of the universe, including the agent’s brain (determinism). This allows deliberacy, but not freedom in the free will sense. So this decision isn't the product of free will.
- The decision is made entirely on the basis of non-deterministic randomness. This allows freedom but not deliberacy. So this decision can't be the product of free will either.
- The decision is partly the product of the prior state of the universe, and partly the product of non-deterministic randomness.
The the case of possibility 3, neither contributing part can be called free will (prior state determinism on the one hand and randomness on the other). A decision making system that combines a bit of each of these doesn’t unlock the elusive power of could have deliberately decided differently either.
An analogy: A traffic control system might behave perfectly predictably given the same input. It makes simple decisions about how to control the stop lights at a junction. We don't get this system any closer to having free will by incorporating the results of a random number generator into its decisions, making them less predictable. This is true even if the RNG could harnesses something like quantum randomness.
What is going on?
We have a blind spot. We can’t be aware of the causes of the thoughts that we experience as the self. So to us these thoughts seem uncaused. Free will is the flattering illusion that the self is an uncaused cause.