Before getting into the main topic, I want to clear up one doubtful point about determinism and probability. The example I gave concerning the evolution of the eye wasn't really very clear, so here is a simpler and (I hope!) better one.
Imagine throwing a hundred sixes in a row with a fair die. The probability of that actually happening is rather small: 1/6100, to be precise. To express that as a decimal, one would need 79 zeroes after the decimal point followed by 15, approximately. Such a series of throws has never occurred since dice were invented, we can be pretty sure. Of course it is the laws of probability that make us feel sure - very improbable events are very unlikely to happen. But if the universe is deterministic, why should this be? Surely a series of one hundred sixes could be determined just as straightforwardly as some more varied series. Why should a deterministic universe behave like a probabilistic one? That is certainly strange, though a proponent of determinism could argue that the laws of probability happen to be among the laws of nature.
That example leads us nicely into indeterminism, in fact. If the universe is not deterministic, what must it be like? Determinism means that future events can be predicted by a precise knowledge of a past state of the universe together with the laws of nature. So indeterminism must mean that at least one event cannot be so predicted. Instead of precisely one state following on from the past, there would be at least two in at least one case. A diagram may help:
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| Here there are three events that may follow some determined "past". This situation ensures indeterminism, for we cannot predict just which event will come to pass. |
Definite probabilities are shown for each of the three possible outcomes, for being able to predict those does not imply determinism. As long as there is any probability at all of more than one outcome, the universe is not deterministic. And of course if at least one of those three possibilities leads on to more than one other, we may end up with a huge number of possible futures.
What about free will in such a scenario? The everyday concept still doesn't look so good. Do we want our free will decisions to be ultimately nothing more than chance events in our brains? Somehow we feel that we can decide something about the future, and that as a result of our decision the universe has to change, even if only in a very tiny way. There is no chance involved in this process.
But in that case, our everyday notion of free will doesn't seem to work in any kind of universe, for what kind could there be that is neither deterministic nor indeterministic? There don't seem to be any other possibilities, given our usual ideas about space and time, anyway. Perhaps we should change our usual ideas, for something indeterministic this time. The result may not be so disturbing as Dennett's version of free will in a deterministic universe. After all, when we think of really important decisions we have made in our lives, might there not be at least an element of chance? We think and think, and read and read, ask our friends for advice, but in the end we just have to leap at one choice or another, and hope we don't come to regret it.
In order to fully grasp what "indeterministic free will" might involve, it may be easiest to start with ethics and morality. They pose a severe problem deterministically, for then, what is the use of any kind of reward or punishment for behaviour? But in a probabilistic universe, there may well be some point to them.
My idea is easiest to see with a diagram, such as the one shown on the next page. The laws of nature are presumed to be at least partly probabilistic, but of course events in the past may change the probabilities of other events occurring in the present or future. At first there is a 50% probability that Alice will perform some altruistic act, and a 50% probability that she will not. If she does not in fact behave altruistically, then Bob also has a 50% probability of performing the same act, and a 50% probability of not doing so. But if Alice happens to be altruistic (and remember this is merely due to chance, and has nothing to do with any free will, which does not exist), there is an 80% probability that she will be rewarded for her action, and just a 20% probability that she will not. Bob will get to know of this, and the chance of his acting altruistically too increases to 90%, leaving a 10% chance of not so acting. On the other hand, if Alice is not rewarded, Bob's enthusiasm might be reduced, so that he then has just a 30% chance of being altruistic, and a 70% of not being so.
Alice acts atruistically just by chance, so in one way it is not right to reward her for her action. Yet her reward may well make a difference to other people's behaviour in the future. The chance of Bob's behaving equally well is increased. The world can get better in that kind of way, in spite of the ultimately random behaviour of individuals. The probability that a person will behave in a certain way depends on some innate brain structure, due to biological chance, plus the ideas accumulated in life. To understand this better, a new concept may be useful, that of the meme.
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