Do We Have Free Will? Part 2: Relativity

As I mentioned last time, there are both causal and non-causal varieties of determinism. Most people think of determinism only in terms of the former: events are determined, they might say, if they are the result of prior states along with strict laws of cause and effect (so that given those prior states and laws, the events could not have failed to occur). But historically there have also been arguments for determinism that have nothing to do with causation, such as logical determinism and the type of theological determinism based on God’s foreknowledge (as opposed to God’s foreordination).

I’ll return to theological determinism next time. Today, I want to talk about a much less well-known kind of non-causal determinism.

According to the theory of relativity, there is no absolute “now,” or present moment. What for you are two simultaneous events won’t necessarily be simultaneous for someone else. So, for instance, take what is going on in a galaxy far, far away at the moment you are reading this. There are events occurring there that, from your perspective, are occurring right now. You can’t know about them yet, of course. If the galaxy is, say, 2.5 million light years away, then you have to wait 2.5 million years for its light to reach us. But if you look at it then, you will see what was happening there at the time you were reading this (approximately). However, you can’t say that those events that for you are occurring right now are occurring right now in any absolute sense — because for someone else right now who is travelling relative to you, what is going on in that galaxy will be some other set of events. But that means the universe as a whole cannot be absolutely divided at each moment into past, present and future.

What does this have to do with determinism? Well, in order for indeterminism to be true, the future must be open to more than one possible “path.” Maybe event E will occur tomorrow, or maybe it won’t. This means the future is unlike the present and the past, which are already settled. But if there isn’t any absolute sense in which something is still future, then it seems one cannot distinguish between the settled past and the open future in this way. What is still future for you at a given moment may already be past for someone else at that same moment. And if it is already settled for them, how can it be anything other than settled for you as well?

Roger Penrose put this idea very clearly in what has come to be known as the Andromeda Paradox:

“Two people pass each other on the street; and according to one of the two people, an Andromedean space fleet has already set off on its journey, while to the other, the decision as to whether or not the journey will actually take place has not yet been made. How can there still be some uncertainty as to the outcome of that decision? If to either person the decision has already been made, then surely there cannot be any uncertainty. The launching of the space fleet is an inevitability. In fact neither of the people can yet know of the launching of the space fleet. They can know only later, when telescopic observations from earth reveal that the fleet is indeed on its way. Then they can hark back to that chance encounter, and come to the conclusion that at that time, according to one of them, the decision lay in the uncertain future, while to the other, it lay in the certain past. Was there then any uncertainty about that future? Or was the future of both people already ‘fixed’?” (The Emperor’s New Mind, 392-393)

In order for free will (in the sense being discussed here) to exist, one must be able to choose from among different possible courses of action. You can either go out tonight or stay home. But if the future is as settled as the past, there is only the one possibility: what will in fact occur. If you stay home, that’s the only thing that you could have done. This view of time is therefore inconsistent with the existence of free will.

The only way to avoid this conclusion, it seems to me, is to reject the relativity of simultaneity.

For more on this kind of determinism, see Relativistic Determinism