Hard Determinism Explained

Everything is predetermined and we have no free will

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Hard determinism is a philosophical position that consists of two main claims:

  1. Determinism is true.
  2. Free will is an illusion.

The distinction between “hard determinism” and “soft determinism” was first made by the American philosopher William James (1842-1910). Both positions insist on the truth of determinism: that is, they both assert that every event, including every human action, is the necessary result of prior causes operating according to the laws of nature. But whereas soft determinists claim that this is compatible with our having free will, hard determinists deny this. While soft determinism is a form of compatibilism, hard determinism is a form of incompatibilism.

Arguments for hard determinism

Why would anyone want to deny that human beings have free will? The main argument is simple. Ever since the scientific revolution, led by the discoveries of people like Copernicus, Galileo, Kepler, and Newton, science has largely presupposed that we live in a deterministic universe. The principle of sufficient reason asserts that every event has a complete explanation. We may not know what that explanation is, but we assume that everything that happens can be explained. Moreover, the explanation will consist of identifying the relevant causes and laws of nature that brought about the event in question.

To say that every event is determined by prior causes and the operation of laws of nature means that it was bound to happen, given those prior conditions. If we could rewind the universe to a few seconds before the event and play the sequence through again, we’d get the same result. Lightning would strike in exactly the same spot; the car would break down at exactly the same time; the goalkeeper would save the penalty in exactly the same way; you would choose exactly the same item from the restaurant’s menu. The course of events is predetermined and therefore, at least in principle, predictable.

One of the best-known statements of this doctrine was given by the French scientist Pierre-Simon Laplace (11749-1827). He wrote:


Science cannot really prove that determinism is true. After all, we often do encounter events for which we don’t have an explanation. But when this happens, we don’t assume that we are witnessing an uncaused event; rather, we just assume that we haven’t discovered the cause yet. But the remarkable success of science, and especially its predictive power, is a powerful reason for supposing that determinism is true. For with one notable exception–quantum mechanics (about which see below) the history of modern science has been a history of the success of deterministic thinking as we have succeeded in making increasingly accurate predictions about everything, from what we see in the sky to how our bodies react to particular chemical substances.

Hard determinists look at this record of successful prediction and conclude that the assumption it rests on–every event is causally determined–is well-established and allows for no exceptions. That means that human decisions and actions are as predetermined as any other event. So the common belief that we enjoy a special sort of autonomy, or self-determination, because we can exercise a mysterious power we call “free will,” is an illusion. An understandable illusion, perhaps, since it makes us feel that we are importantly different from the rest of nature; but an illusion all the same.

What about quantum mechanics?

Determinism as an all-encompassing view of things received a severe blow in the 1920s with the development of quantum mechanics, a branch of physics dealing with the behavior of subatomic particles. According to the widely accepted model proposed by Werner Heisenberg and Niels Bohr, the subatomic world contains some indeterminacy. For instance, sometimes an electron jumps from one orbit around its atom’s nucleus to another orbit, and this is understood to be an event without a cause. Similarly, atoms will sometimes emit radioactive particles, but this, too, is viewed as an event without a cause. Consequently, such events cannot be predicted. We can say that there is, say, a 90% probability that something will happen, meaning that nine times out of ten, a specific set of conditions will produce that happening. But the reason we can’t be more precise is not because we are lacking a relevant piece of information; it is just that a degree of indeterminacy is built into nature.

The discovery of quantum indeterminacy was one of the most surprising discoveries in the history of science, and it has never been universally accepted. Einstein, for one, could not countenance it, and still today there are physicists who believe that the indeterminacy is only apparent, that eventually a new model will be developed which reinstates a thoroughly deterministic point of view. At present, though, quantum indeterminacy is generally accepted for much the same sort of reason that determinism is accepted outside quantum mechanics: the science that presupposes it is phenomenally successful.

Quantum mechanics may have dented the prestige of determinism as a universal doctrine, but that doesn’t mean it has salvaged the idea of free will. There are still plenty of hard determinists around. This is because when it comes to macro objects like human beings and human brains, and with macro events such as human actions, the effects of quantum indeterminacy is thought to be negligible to non-existent. All that is needed to rule out free will in this realm is what is sometimes called “near determinism.” This is what it sounds like–the view that determinism holds throughout most of nature. Yes, there may be some subatomic indeterminacy. But what is merely probabilistic at the subatomic level still translates into deterministic necessity when we are talking about the behavior of larger objects.

What about the feeling that we have free will?

For most people, the strongest objection to hard determinism has always been the fact that when we choose to act in a certain way, it feels as if our choice is free: that is, it feels as if we are in control and exercising a power of self-determination. This is true whether we are making life-altering choices such as deciding to get married, or trivial choices such as opting for apple pie rather than cheesecake.

How strong is this objection? It is certainly convincing to many people. Samuel Johnson probably spoke for many when he said, “We know our will is free, and there’s an end to it!” But the history of philosophy and science contains many examples of claims that seem obviously true to common sense but turn out to be false. After all, it feels as if the earth is still while the sun moves around it; it seems as if material objects are dense and solid when in fact they consist mainly of empty space. So the appeal to subjective impressions, to how things feel is problematic.

On the other hand, one could argue that the case of free will is different from these other examples of common sense being wrong. We can accommodate the scientific truth about the solar system or the nature of material objects fairly easily. But it’s hard to imagine living a normal life without believing that you are responsible for your actions. The idea that we are responsible for what we do underlies our willingness to praise and blame, reward and punish, take pride in what we do or feel remorse. Our whole moral belief system and our legal system seem to rest on this idea of individual responsibility.

This points to a further problem with hard determinism. If every event is causally determined by forces beyond our control, then this must include the event of the determinist concluding that determinism is true. But this admission seems to undermine the whole idea of arriving at our beliefs through a process of rational reflection. It also seems to render pointless the whole business of debating issues like free will and determinism, since it is already predetermined who will hold what view. Someone making this objection doesn’t have to deny that all our thought processes have correlated physical processes going on in the brain. But there is still something odd about treating one’s beliefs as the necessary effect of these brain processes rather than as the result of reflection. On these grounds, some critics view hard determinism as self-refuting.

Related links

Indeterminism and free will