Our fate in whose hands?

PUBLISHED : Saturday, 20 November, 1993, 12:00am
UPDATED : Saturday, 20 November, 1993, 12:00am

IN the play Julius Caesar, Cassius tells Brutus: ''Men at some time are masters of their fate.'' But are we really masters of our fate? Or is everything we do determined and preordained? The argument for preordination used to be that God was omnipotent and outside time, so God would know what was going to happen. But how then could we have any free will? And if we don't have free will, how can we be responsible for our actions? It can hardly be one's fault if one has been preordained to rob a bank. So why should one be punished for it? In recent times, the argument for determinism has been based on science. It seems that there are well-defined laws that govern how the universe and everything in it develops in time.

Although we have not yet found the exact form of all these laws, we already know enough to determine what happens in all but the most extreme situations. Whether we will find the remaining laws in the fairly near future is a matter of opinion.

I'm an optimist: I think there's a fifty-fifty chance that we will find them in the next 20 years. But even if we don't, it won't really make any difference to the argument.

The important point is that there should exist a set of laws that completely determines the evolution of the universe from its initial state. These laws may have been ordained by God. But it seems that He (or She) does not intervene in the universe to break the laws.

The initial configuration of the universe may have been chosen by God or it may itself have been determined by the laws of science. In either case, it would seem that everything in the universe would then be determined by evolution according to the laws of science, so it is difficult to see how we can be masters of our fate.

The idea that there is some grand unified theory that determines everything in the universe raises many difficulties. First of all, the grand unified theory is presumably compact and elegant in mathematical terms. There ought to be something special and simple about the theory of everything. Yet how can a certain number of equations account for the complexity and trivial detail that we see around us? Can one really believe that the grand unified theory has determined that Sinead O'Connor will be the top of the hit parade this week or that Madonna will be on the cover of Cosmopolitan ? A second problem with the idea that everything is determined by a grand unified theory is that anything we say is also determined by the theory. But why should it be determined to be correct? Isn't it more likely to be wrong, because there are many possible incorrect statements for every true one? Each week, the mail contains a number of theories that people have sent me. They are all different and most are mutually inconsistent. Yet presumably the grand unified theory has determined that the authors think they were correct. So why should anythingI say have any greater validity? Am I not equally determined by the grand unified theory? A third problem with the idea that everything is determined is that we feel that we have free will - that we have the freedom to choose whether to do something. But if everything is determined by the laws of science then free will must be an illusion, and if we don't have free will what is the basis for our responsibility for our actions? We don't punish people for crimes if they are insane, because we have decided that they can't help it. But if we are all determined by a grand unified theory, none of us can help what we do, so why should anyone be held responsible for what they do? These problems of determinism have been discussed over the centuries. The discussion was somewhat academic, however, as we were far from a complete knowledge of the laws of science and we didn't know how the initial state of the universe was determined.

The problems are more urgent now because there is the possibility that we may find a complete unified theory in as little as 20 years. And we realise that the initial state may itself have been determined by the laws of science. What follows is my personal attempt to come to terms with these problems. I don't claim any great originality or depth but it is the best I can do at the moment.

To start with the first problem: how can a relatively simple and compact theory give rise to a universe that is as complex as the one we observe, with all its trivial and unimportant details? The key to this is the uncertainty principle of quantum mechanics which states that one cannot measure both the position and speed of a particle to great accuracy; the more accurately you measure the position, the less accurately you can measure the speed, and vice versa.

This uncertainty is not so important at the present time, when things are far apart, so that a small uncertainty in position does not make much difference. But in the very early universe, everything was very close together, so there was quite a lot of uncertainty and there were a number of possible states for the universe.

These different possible early states would have evolved into a whole family of different histories for the universe. Most of these histories would be similar in their large-scale features. They would correspond to a universe that was uniform and smooth,and that was expanding.

However, they would differ on details like the distribution of stars and, even more, on what was on the covers of their magazines. (That is, if those histories contained magazines.) Thus the complexity of the universe around us and its details arose from the uncertainty principle in the early stages. This gives a whole family of possible histories for the universe. There would be a history in which the Nazis won World War II though the probability is low. But we just happen to live in a history in which the Allies won the war and Madonna was on the cover of Cosmopolitan.

I now turn to the second problem: if what we do is determined by some grand unified theory, why should the theory determine that we draw the right conclusions about the universe rather than the wrong ones? Why should anything we say have any validity? My answer to this is based on Darwin's idea of natural selection. I take it that some very primitive form of life arose spontaneously on Earth from chance combinations of atoms. This early form of life was probably a large molecule. But it was probably not DNA, since the chances of forming a whole DNA molecule by random combinations are small.

The early form of life would have reproduced itself. The quantum uncertainty principle and the random thermal motions of the atoms would mean that there were a certain number of errors in the reproduction. Most of these errors would have been fatal to the survival of the organism or its ability to reproduce.

Such errors would not be passed on to future generations but would die out. A very few errors would be beneficial, by pure chance. The organisms with these errors would be more likely to survive and reproduce. Thus they would tend to replace the original, unimproved organisms.

The development of the double helix structure of DNA may have been one such improvement in the early stages. This was probably such an advance that it completely replaced any earlier form of life, whatever that may have been. As evolution progressed, it would have led to the development of the central nervous system.

Creatures that correctly recognised the implications of data gathered by their sense organs and took appropriate action would be more likely to survive and reproduce. The human race has carried this to another stage. We are very similar to higher apes, both in our bodies and in our DNA; but a slight variation in our DNA has enabled us to develop language.

This has meant that we can hand down information and accumulate experience from generation to generation, in spoken and eventually in written form. Previously, the result of experience could be handed down only by the slow process of it being encoded into DNA through random errors in reproduction.

THE effect has been a dramatic speed-up of evolution. It took more than three billion years to evolve up to the human race. But in the course of the past 10,000 years, we have developed written language. This has enabled us to progress from cave dwellers to the point where we can ask about the ultimate theory of the universe.

There has been no significant biological evolution, or change in human DNA, in the past 10,000 years. Thus, our intelligence, our ability to draw the correct conclusions from the information provided by our sense organs, must date back to our cave-dweller days or earlier. It would have been selected for on the basis of our ability to kill certain animals for food and to avoid being killed by other animals.

It is remarkable that mental qualities that were selected for these purposes should have stood us in such good stead in the very different circumstances of the present day. There is probably not much survival advantage to be gained from discovering a grand unified theory or answering questions about determinism. Nevertheless, the intelligence that we have developed for other reasons may well ensure that we find the right answers to these questions.

I now turn to the third problem, the questions of free will and responsibility for our actions. We feel subjectively that we have the ability to choose who we are and what we do. But this may just be an illusion. Some people think they are Jesus Christ or Napoleon, but they can't all be right.

What we need is an objective test that we can apply from the outside to distinguish whether an organism has free will. For example, suppose we were visited by a ''little green person'' from another star. How could we decide whether it had free will or was just a robot, programmed to respond as if it were like us? The ultimate objective test of free will would seem to be: can one predict the behaviour of the organism? If one can, then it clearly doesn't have free will but is predetermined. On the other hand, if one cannot predict the behaviour, one could take thatas an operational definition that the organism has free will.

One might object to this definition of free will on the grounds that once we find a complete unified theory we will be able to predict what people will do. The human brain, however, is also subject to the uncertainty principle. Thus, there is an element of the randomness associated with quantum mechanics in human behaviour. But the energies involved in the brain are low, so quantum mechanical uncertainty is only a small effect.

The real reason why we cannot predict human behaviour is that it is just too difficult. We already know the basic physical laws that govern the activity of the brain, and they are comparatively simple. But it is just too hard to solve the equations when there are more than a few particles involved.

Even in the simpler Newtonian theory of gravity, one can solve the equations exactly only in the case of two particles. For three or more particles one has to resort to approximations, and the difficulty increases rapidly with the number of particles. The human brain contains about a hundred million billion billion particles. This is far too many for us ever to be able to solve the equations and predict how the brain would behave, given its initial state and the nerve data coming into it.

In fact, of course, we cannot even measure what the initial state was, because to do so we would have to take the brain apart. Even if we were prepared to do that, there would just be too many particles to record.

Also, the brain is probably very sensitive to the initial state - a small change in the initial state can make a very large difference to subsequent behaviour. So although we know the fundamental equations that govern the brain, we are quite unable to use them to predict human behaviour.

This situation arises in science whether or not we deal with the macroscopic system, because the number of particles is always too large for there to be any chance of solving the fundamental equations.

What we do instead is use effective theories. These are approximations in which the very large number of particles are replaced by a few quantities. An example is fluid mechanics.

A liquid such as water is made up of billions of billions of molecules that themselves are made up of electrons, protons, and neutrons. Yet it is a good approximation to treat the liquid as a continuous medium, characterised just by velocity, density, and temperature. The predictions of the effective theory of fluid mechanics are not exact - one only has to listen to the weather forecast to realise that - but they are good enough for the design of ships or oil pipelines.

I want to suggest that the concepts of free will and moral responsibility for our actions are really an effective theory in the sense of fluid mechanics.

It may be that everything we do is determined by some grand unified theory. If that theory has determined that we shall die by hanging, then we shall not drown. But you would have to be awfully sure that you were destined for the gallows to put to sea ina small boat during a storm.

I HAVE noticed that even people who claim that everything is predestined and that we can do nothing to change it look before they cross the road. Maybe it's just that those who don't look don't survive to tell the tale.

One cannot base one's conduct on the idea that everything is determined, because one does not know what has been determined. Instead, one has to adopt the effective theory that one has free will and that one is responsible for one's actions.

This theory is not very good at predicting human behaviour, but we adopt it because there is no chance of solving the equations arising from the fundamental laws. There is also a Darwinian reason that we believe in free will: a society in which the individual feels responsible for his or her actions is more likely to work together and survive to spread its value.

Of course, ants work well together, but such a society is static. It cannot respond to unfamiliar challenges or develop new opportunities. A collection of free individuals who share certain mutual aims, however, can collaborate on their common objectivesand yet have the flexibility to make innovations. Thus, such a society is more likely to prosper and to spread its system of values.

The concept of free will belongs to a different arena from that of fundamental laws of science. If one tries to deduce human behaviour from the laws of science, one gets caught in the logical paradox of self-referencing systems.

If what one does could be predicted from the fundamental laws, then the fact of making that prediction could change what happens. It is like the problems one would get into if time travel were possible, which I don't think it ever will be.

If you could see what is going to happen in the future, you could change it. If you knew which horse was going to win the Grand National, you could make a fortune by betting on it. But that action would change the odds. One only has to see Back to the Future to realise what problems could arise.

This paradox about being able to predict one's actions is closely related to the problem I mentioned earlier: will the ultimate theory determine that we come to the right conclusions about the ultimate theory? In that case, I argued that Darwin's idea ofnatural selection would lead us to the correct answer.

Maybe the correct answer is not the right way to describe it, but natural selection should at least lead us to a set of physical laws that work fairly well.

However, we cannot apply those physical laws to deduce human behaviour for two reasons. First, we cannot solve the equations. Second, even if we could, the fact of making a prediction would disturb the system. Instead, natural selection seems to lead to us adopting the effective theory of free will.

If one accepts that a person's actions are freely chosen, one cannot then argue that in some cases they are determined by outside forces. The concept of ''almost free will'' doesn't make sense. But people tend to confuse the fact that one may be able to guess what an individual is likely to choose with the notion that the choice is not free.

One example of such confusion is the doctrine of diminished responsibility: the idea that persons should not be punished for their actions because they were under stress.

It may be that someone is more likely to commit an anti-social act when under stress. But that does not mean that we should make it even more likely that he or she commit the act by reducing the punishment.

One has to keep the investigation of the fundamental laws of science and the study of human behaviour in separate compartments. One cannot use the fundamental laws to deduce human behaviour, for the reasons I have explained. But one might hope that we could employ both the intelligence and the powers of logical thought that we have developed through natural selection.

Unfortunately, natural selection has also developed other characteristics, such as aggression. Aggression would have given a survival advantage in cave-dweller days and earlier and so would have been favoured by natural selection. The tremendous increase in our powers of destruction brought about by modern science and technology, however, has made aggression a very dangerous quality, one that threatens the survival of the whole human race.

The trouble is, our aggressive instincts seem to be encoded in our DNA. DNA changes by biological evolution only on a time scale of millions of years, but our powers of destruction are increasing on a time scale of the evolution of information, which is now only 20 or 30 years.

Unless we can use our intelligence to control our aggression, there is not much chance for the human race. Still, while there's life, there's hope.

To recapitulate: I have discussed some of the problems that arise if one believes that everything in the universe is determined. It doesn't make much difference whether this determinism is due to an omnipotent God or to the laws of science. Indeed, one could always say that the laws of science are the expression of the will of God.

I considered three questions: first, how can the complexity of the universe and all its trivial details be determined by a simple set of equations? Alternatively, can one really believe that God chose all the trivial details, like who should be on the cover of Cosmopolitan ? The answer seems to be that the uncertainty principle of quantum mechanics means that there is not just a single history for the universe but a whole family of possible histories. These histories may be similar on very large scales, but they will differ greatly on normal, everyday scales.

We happen to live on one particular history that has certain properties and details. But there are very similar intelligent beings who live on histories that differ in who won the war and who is Top of the Pops. Thus, the trivial details of our universe arise because the fundamental laws incorporate quantum mechanics with its element of uncertainty or randomness.

The second question was: if everything is determined by some fundamental theory, then what we say about the theory is also determined by the theory - and why should it be determined to be correct, rather than just plain wrong or irrelevant? My answer to this was to appeal to Darwin's theory of natural selection: only those individuals who drew the appropriate conclusions about the world around them would be likely to survive and reproduce.

The third question was: if everything is determined, what becomes of free will and our responsibility for our actions? But the only objective test of whether an organism has free will is whether its behaviour can be predicted.

In the case of human beings, we are quite unable to use the fundamental laws to predict what people will do, for two reasons. First, we cannot solve the equations for the very large number of particles involved. Second, even if we could solve the equations, the fact of making a prediction would disturb and could lead to a different outcome. So as we cannot predict human behaviour, we may as well adopt the effective theory that humans are free agents who can choose what to do.

It seems that there are definite survival advantages to believing in free will and responsibility for one's actions. That means this belief should be reinforced by natural selection.

Whether the language-transmitted sense of responsibility is sufficient to control the DNA-transmitted instinct of aggression remains to be seen. If it does not, the human race will have been one of natural selection's dead ends.

Maybe some other race of intelligent beings elsewhere in the galaxy will achieve a better balance between responsibility and aggression. But if so, we might have expected to be contacted by them, or at least to detect their radio signals. Maybe they are aware of our existence but don't want to reveal themselves to us. That might be wise, given our record.

In summary, the question is: is everything determined? The answer is yes, it is. But it might as well not be, because we can never know what is determined.

Stephen Hawking 1993 Extract taken from Black Holes and Baby Universes and Other Essays by Stephen Hawking. Published by Bantam.


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