This is the fortieth post in my Theories of Knowledge and Reality series. Follow the link for more on the series and for links to other entries as they appear. In the last post, I looked at some of the arguments that have been offered in favor of taking ourselves to have free will. In this post, I'd like to distinguish between the different views one can take on the two main issues at stake in this debate, with some attention to which combinations of these views are coherent.
I've already given a definition of determinism, and its denial is indeterminism. If the laws of nature and any state of the world guarantee any later state of the world, then determinism is true. Otherwise, indeterminism is true. The question that immediately arises is how we should connect that issue up with the question of free will. To settle that, we first need an account of what free will is, and then we can answer the question of whether we could be free in a world that is deterministic. In a coinage that, unusual for philosophy, actually reflects ordinary, contemporary English, the view that freedom and determinism are compatible is called compatibilism. Thus some views of freedom will be compatibilist accounts of freedom, while others will be incompatibilist.
Incompatibilism splits into two main camps, libertarianism and hard determinism. Both affirm that we can't have free will if determinism is true, but each chooses a different horn of the dilemma. Libertarians (not to be confused with political libertarians) affirm human freedom and deny determinism, while hard determinists accept determinism and deny free will. The standard libertarian account of freedom includes at least one thesis, sometimes called the Principle of Alternative Possibilities (PAP). PAP says that it is possible to do otherwise than what we actually do. Whatever we did do, we could have done something else. We'll look at some variations in what else a libertarian might say, but most libertarians do accept this component. For now it will suffice to see that if determinism is true, then only one future seems possible, since the laws of nature together with the past will guarantee the future, exactly one future, without other options for what that future will be. So if determinism is true, then we seem not to have alternative options. Thus freedom requires indeterminism if libertarianism is correct.
It is important to point out that hard determinism does not hold to a stronger version of determinism than other determinists. The determinism held by hard determinists is the same determinism I've been discussing all along in this series. What makes it hard determinism is its denial of freedom. Determinists who don't deny free will are called soft determinism, not because their determinism is softer but because they are compatibilists and thus can affirm human freedom as real. Soft determinism and compatibilism aren't technically the same thesis. Compatibilists hold that freedom is compatible with determinism. They don't necessarily hold determinism to be true. If they accept both theses, then they are soft determinists.
A hard determinist argues that determinism is true and therefore we don’t have freedom. This involves a deterministic account of human action. Our beliefs and desires come from things outside our control, e.g. genetics or upbringing. If you trace back far enough, you can see that the way we are determines what we do, and the way we are goes back to things that were never under our control. So determinism is true, and we’re not free. Science is in the business of giving explanations, and if we try to say we act in freedom without explanation, it seems to go against science.
The hard determinist says we choose, just not freely. We see what seem to be options, and we choose one. It’s just that the one we choose is the only possible choice. The others aren’t genuine possibilities. We could never know what we’ll do, since the causes of our actions are usually very complicated and not available to our conscious thoughts, but that doesn’t mean they’re not predetermined.
The compatibilist, on the other hand, tries to argue that we can be free even if we’re predetermined. They will say freedom doesn’t require the ability to do otherwise. It requires something less strong, something we can have if determinism is true. In later posts, we'll look at some particular strategies have for trying to fit their weaker accounts of freedom together with what we ordinarily believe about freedom.
Technically speaking, there are other possible views. There are compatibilists who aren't determinists. They just think that the kind of freedom we have is compatible with determinism, even if determinism is false. Sometimes it's because they believe something close enough to determinism is true that we wouldn't be free if incompatibilist accounts of freedom are correct.
Alternatively, you might also encounter those who think freedom requires being caused in a way like what would happen if determinism is true. But then they don't think determinism is true, and so we aren't free. Or you might find people who think incompatibilism is correct, and we can't be free if determinism is true, but they don't happen to think whatever is required for freedom is true. In other means, indeterminism isn't sufficient for freedom, and whatever further is required is not true.
But the three main views in the history of this debate are incompatibilist hard determinism, compatibilist soft determinism, and incompatibilist libertarianism, and even hard determinists are few and far between. Libertarianism and compatibilism will be my focus in the remaining posts of this series. I will mention other possibilities only in one or two places when they are relevant for particular arguments I'll be discussing.