Principle of Determinism

The principle is that every event has a cause.

In the end, Ayer rejects the principle, but he also thinks that most of the standard arguments against it have been wrong, and miss the point.

So, first, the standard arguments, and what Ayer thinks is wrong with them.

The first is the argument from miracles. It goes, since there have been miracles, there are no universal necessary causal principles. Ayer says that the idea behind this criticism is mistaken, quite independently of whether or not there have in fact been miracles, so let’s not worry about that. The idea behind this argument is that causal laws are divinely imposed, and that God can, and has, suspended them from time to time. It is straightforwardly animistic, and we have seen that no tenable notion of causation can have such a component anyhow. A causal law must be a correlation that always holds, and so all that a miracle could show is that something that looked like it was a causal law in fact isn’t.

Side remark: I am discussing this, as Ayer pretty much does, in terms of the idea, not of constant conjunction, which is Ayer’s official theory, but in terms of causation in accordance with laws, the theory I outlined. Ayer seems to have implicitly switched.

Second argument: Freedom of will. If all of our actions are determined we have no free will, and hence no moral responsibility, which, it is to be assumed, is absurd. As a matter of fact, if our actions happened without causes, then even we wouldn’t be causes of them. It is only because actions are events with causes, namely events caused by us, that there can be moral responsibility. Far from being inconsistent with moral responsibility, some causal determinism is required for their to be moral responsibility. In general, we take someone to be morally responsible for an action if that person performed that action in accordance with that persons beliefs, desires, and intentions, even though those beliefs, desires, and intentions may have some previous external origins. Of course, this can be matter of degree: even if someone does something intentionally, they may not responsible if, for example, they have been brainwashed. However, you are morally responsible for your actions even though your beliefs, desires, and intentions have been to some extent shaped by factors external to you.

Quantum indeterminacy has also been taken to be an argument against the principle of determinism. Here the situation is a little more complicated. First, I have to say something about quantum mechanics (QM). QM is a generally accepted physical theory. According to it, certain kinds of events, even given all knowledge of the positions, momenta, and all other physical quantities that could ever be measured about everything in the universe, are still irreducibly probabilistic. For example, the probability that a given radioactive atom will decay in some fixed period of time is an irreducible probability: even with complete knowledge of all measurable quantities about that atom and everything else, you still can’t get more than a probability.

One argument for the principle of determinism has been that it is inconceivable, or humanly inconceivable, that it not hold. That is, the claim is that the world cannot be made sense of unless the principle is true. QM shows that that argument is wrong.

On the other hand, QM does not show that the principle of determinism is false: perhaps everything is fully determined according to causal laws, but only based on what are now called hidden variables: facts about the world that are not accessible to measurement. The apparent failure of determinism in QM only results from a further decision to stick with measurable quantities. Ayer just conjectures that this might be the case, but David Bohm, in the 1950s, actually showed that such a version of QM is possible.

OK. The usual arguments against the principle of determinism fail.

But, is the principle true? It claims that every event has a cause, which means that for every event there is another such that the first is brought about by it according to necessary law. This seems to be an empirical claim. Some would argue that the spectacular success of science seems to show it true. But of course, most of what actually occurs cannot in fact be explained today in terms of laws. As an empirical claim, we are far from having strong reason to believe in the principle. Some scientifically minded people would say that it is defeatist to accept that some events have no cause, it just to give up on understanding why and how they occur. Ayer is prepared to agree with that, but it is not an assertion of the principle of determinism, but an assertion of the maxim of determinism: it is a good idea for the advancement of knowledge to assume that the principle of determinism holds. Maybe so, but that is quite different from an argument that the principle is true.

-- ShaughanLavine - 07 Mar 2003