An advocate of determinism can be supporting to one of two things. The first is a specific kind of physical laws, where each initial state has only a single possible successor state at any given future time. The second is the denial of a certain kind of free will. The first is philosophically irrelevant because it is a purely scientific matter concerning what the best mathematical model for describing observed events is. So it is the second that I care about. And with respect to the second some claim that quantum mechanics somehow refutes it. I of course am committed to them being wrong about that, because I am committed to the claim that philosophy is completely independent of scientific fact, which means that a scientific discovery can neither support nor refute a truly philosophical claim.
But before I can discuss that matter it is first necessary to talk a bit about what free will is. There are many definitions of free will. Some, including myself, take free will to be essentially the power of self-determination or self-causation. In other words, you are free if you are the primary cause of your own actions. This fits nicely with a physicalist view of the world, since in it you are identified with your brain, and it is obvious that your brain could be considered a primary cause of your actions. Such a view is a compatibilist view, because it entails that the question of whether we have free will is independent of whether the universe is deterministic.
Despite my inclinations that is not the definition of free will that I will be using here. Compatibilism in many ways is the antithesis of the determinism-indeterminism debate because it denies any significance to it. To really engage in that debate we need to make free will part of the stakes. So what is free will in the context of this debate? Many characterize it as “the ability to do otherwise”, but obviously that definition doesn’t say much since it could just as well be used to describe the self-determination view of free will. What is meant by this definition is that to be free one must have the ability to make a meaningful choice which is not fully determined by the preceding physical facts. In other words, one must have the ability to be an uncaused cause (interestingly giving people a property that was classically reserved for the divine).
Obviously in a Newtonian world-view there is no room for such a thing. Every event is caused and completely determined by preceding events. Which means that either the choices of individuals are determined in this way, making them un-free, or their choices are somehow made outside the physical world and cannot have any causal import. Either way free will is an impossibility. Quantum physics changes the Newtonian picture of the world. In it there appears to be room for randomness. Moreover it appears that this randomness is somehow connected to people, because observers are credited with collapsing the wave-function, which is what gives rise to it. And some take this to make room for the exercise of free will.
The first objection that could be raised against this leap in logic is that this is simply one interpretation of quantum mechanics. And it is a very problematic one. Most interpretations that try to overcome its problems either get rid of the collapse of the wave-function or get rid of the observer’s role in that collapse. But let’s be a charitable as we can and stick with this interpretation of quantum mechanics. Even so it still doesn’t give the supporter of free will what they want. It opens the door for the possibility of events that aren’t fully determined by preceding events, and that is part of what is required for free-will, but it doesn’t leave room for a meaningful choice to be behind it, which is the other part. Perhaps I should elaborate. In quantum mechanics it is certainly true that the collapse of the wave-function happens in a way that is not completely determined by preceding events. But the collapse is also completely random. The fact that the collapse is random means that we do not have any control over it, because that would be the opposite of random. In other words this randomness is not a place where choice can have an effect. But perhaps the observer’s role in sparking collapse is where their choice enters into the picture. Alas, this cannot be the case either: observers don’t have a choice about whether they cause the wave-function to collapse, they always cause it to collapse.
In summary: quantum mechanics refutes the first of the two claims “determinism” might be a label for, as described in the first paragraph. Namely it may, under certain interpretations, be incompatible with certain ways of mathematically modeling the universe. But it has no bearing on the second claim, namely the denial of effective uncaused choices. In fact I would go so far as to say that it is impossible for any scientific theory to lend credibility to the existence of free will, so defined. Because every theory in physics will model the world using laws. And the laws of physics will make predictions about events. Those predictions will be precise, in which case the events are completely determined, or they will be statistical, in which case the actual course of events will be random and independent of human choice. Either way there is no room for uncaused causes within the course of events described by such laws; an uncaused cause is necessarily outside of any such laws.
Everything I have said so far has been a negative claim; I have been arguing that an appeal to physics, even quantum physics, cannot justify this sort of free will. But in the process of doing so I have been playing that game which I despise so much, namely pretending that scientific findings have some bearing on this issue. I have been pretending they have some bearing to show that, even under all the assumptions made by the advocates of this sort of free will, even assuming it was Newtonian physics that was the biggest obstacle to this sort of free will (which it isn’t, since, again, philosophy is independent from scientific theories), it still cannot be justified by appeals to quantum physics. Now I am going to stop playing that game – I’m going to stop being a bad role model – and describe how this sort of free will can be argued for and against independently of scientific theories.
The question of free will is really one of how we choose understand the choices that we make and that others make, not the forces behind them (how we choose to constitute them). The forces behind them are irrelevant from a philosophical perspective. Because even if we live in a deterministic universe it doesn’t make any difference to us. I don’t know all the relevant physical facts about previous states of the universe – in fact I can’t know them – and thus I will never be in a position to be able to predict with complete accuracy the choices of other people. In other words, as far as I am able to know there will never be any contradiction in taking myself and others to have free will of the “uncaused cause” sort, even if such a thing is physically impossible. But neither does this mean that I must take them to have free will of this sort. Philosophically we have a choice, we are faced with the question: “what is the best way to conceive of the ability of ourselves and others to make choices?”
The “uncaused cause” conception of free will emphasizes the randomness and unpredictability of people’s choices. It emphasizes their “radical freedom”, their ability to make choices that go against everything that they have previously done and said. In contrast the “self-determination” conception emphasizes the connection between our free choices and responsibility. It emphasizes that when our choices are free that we have to own up to them. I can see both conceptions of free choice as being philosophically interesting. So described the “uncaused cause” conception of free will would fit nicely with a theory that was trying to encourage people to make radical choices and to fully exercise their freedom. Using this conception of free will is one way to emphasize to people that they are free to make a break with their past, their past choices, and their past conception of themselves. The “self-determination” conception of free will can be used to good effect in a theory where we are trying to motivate certain kinds of behavior on the basis of someone’s desire to see themselves as free. Kant’s ethics, specifically the Groundwork, is a good example of this. From the conception of ourselves as free agents we are supposed to concede that we are autonomous, and thus self-determining, and that the only way to be autonomous is to govern ourselves with reason.
Obviously it’s not my intention to develop theories based on either of these two conceptions of free will, or the many unnamed alternatives, here. The point is merely to demonstrate that it is possible to have a lively philosophical discussion about them without having to appeal to science. In fact I think that we are far better off without dragging science into it. Because as I have framed this possible debate it is one that is going to involve philosophical systems, as we evaluate different conceptions of human choice and free will based on how they are philosophically useful. I think that this is much more interesting than deriving philosophical consequences from something that is itself unphilosophical, but maybe that’s just me.