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|Publisher:||University of Chicago Press|
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The Possibility of Free Will
By Julian Baggini
The University of Chicago PressCopyright © 2015 Julian Baggini
All rights reserved.
To understand what free will is and why it is under threat, we are going to need to look beyond merely theoretical debates and into the real world. But before we do that, we have to understand the armchair philosophical arguments that have brought the debate to where it is now. There is no better starting point for this than two hundred years ago, when the French mathematician Pierre-Simon Laplace asked what would happen if a vast intellect were to know every law of nature and everything about the state of every object in the universe. The answer would seem to be obvious: like God, it would know all that is, all that had been and all that is to come.
'We may regard the present state of the universe as the effect of its past and the cause of its future,' wrote Laplace.
An intellect which at a certain moment would know all forces that set nature in motion, and all positions of all items of which nature is composed, if this intellect were also vast enough to submit these data to analysis, it would embrace in a single formula the movements of the greatest bodies of the universe and those of the tiniest atom; for such an intellect nothing would be uncertain and the future just like the past would be present before its eyes.
That intellect has become known as known as Laplace's Demon. Ever since Laplace formulated this hypothesis, philosophers have been haunted by what appears to follow from it. This can be captured in a chain of reasoning that is easy to grasp, disturbing in its consequences but seemingly unavoidable: if everything that happens in the physical universe is the result of prior physical causes and effects, then ultimately everything I do must also be the result of prior physical causes and effects. Everything I say and do is caused by events in my brain, which are themselves caused by other events in my past. Free will has disappeared. Like the weather, what I do may be somewhat unpredictable and sometimes appear fickle, but behind it all is simply the motion of matter, the playing out of the laws of physics.
The key implication of Laplace's thought experiment for free will is easily misunderstood. Many people assume that the most important element in it is the predictability of the future. Free will is challenged because if you can predict with one hundred per cent certainty what will happen, there is no role for freedom to make a difference.
Predictability, however, is not the threat to free will that many take it to be. We can see this in the argument that God's omniscience undermines free will. If God knows everything that has been, is and will be, then he knows everything that you will do. But that would seem to suggest that the future is set, and so you can do nothing to change it. And if you can do nothing to change the future, you have no free will.
This inference seems to me to be wrong. God may simply be able to look ahead and see what you will freely choose to do. Why is that fundamentally different from being able to look back into the past and see what you have already freely chosen to do? God's omniscience merely requires him to be able to jump around in time and so need in no way entail that the future is fixed. Augustine summed this up neatly back in the fourth century: 'Although God foreknows what we are going to will in the future, it does not follow that we do not will by the will. Your blameworthy will ... does not cease to be a will simply because God foreknows that you are going to have it.'
The obvious objection to this is that if God knows what you will do tomorrow, then tomorrow must in some way already be fixed, and that is what undermines free will. But I think this plays on an ambiguity in what 'fixed' means here. If we assume that there is only one past, one present and one future, then once anything is done, history is fixed. We do not believe that therefore nothing in the past was done freely, as we believe that things might have happened differently. The only difference between us and God is that he is able to fast-forward and see what will happen as well as rewind to see what has happened. Of course, there is only one tape to fast-forward, so it might look as though the future is 'fixed'. But just as rewinding allows us to see what people freely chose, even though there is only one tape and one thing they did choose, so fast-forwarding can allow us to see what they will choose, even though there can only ever be one thing they will choose.
In short, there are always many things that could happen but only one that does. To be able to see the future is simply to see the one course of events that transpires. That is no more a reason to believe free will makes no difference to the future as to believe it made no difference to the past.
Although I'm confident this argument is sound, it doesn't matter much for those of us who don't believe in an all-knowing God anyway. (Those who do might also reflect that most supposedly divinely inspired texts seem to assume we do make at least some free choices, so there must be something wrong in the idea that God's existence makes them impossible.) What matters more than predictability for naturalists — those of us who believe that the natural world is all there is and no supernatural forces exist — is whether or not the laws of nature make future events inevitable. On this point, naturalists have a free will bogeyman as phoney as the theists' all-knowing God, one that goes by the name of determinism.
Determinism is essentially the thesis that Laplace's demon is a theoretical possibility. We may not know enough ever to predict the future with any great certainty, but the universe is essentially a kind of machine operating according to inviolable laws. And that means everything that happens must happen as a result of the playing out of these laws. To use a somewhat outdated image, atoms bounce off each other, bind to each other, repel and attract each other, and every thing we see, from grass growing to composers writing music, is at bottom the inevitable consequence of matter reacting to matter. Similarly, your thoughts and actions are produced by a brain which is just a complicated biological machine, which, like all such mechanisms, from broccoli to fruit flies, requires no free will to make it work.
The contemporary American philosopher Peter van Inwagen has summed up the challenge of determinism to free will in his version of something called the Consequence Argument. 'If determinism is true, then our acts are the consequence of laws of nature and events in the remote past,' he argues. Since 'it's not up to us what went on before we were born, and neither is it up to us what the laws of nature are', it would therefore follow that 'the consequences of these things (including our present acts) are not up to us'. And it just seems obvious that we cannot be responsible for what is not up to us.
Neuroscientist David Eagleman explained to me why he, like many others, sees determinism as lying at the heart of the free will problem. 'If you're looking at the brain, we always study it as a deterministic system: where this goes off, that trips off that neurotransmitter, that causes this to be polarised, and everything happens lock-step from everything else. The heart of the issue is, given that system, it seems hard to figure out how to slip anything else into there.'
Some have sought to save free will by denying Laplacian determinism. Chaos theory appears to offer a scientific way of doing this. Chaos theory says that complete predictability in physical systems is in practice impossible because even very tiny changes in initial conditions can lead to very different final outcomes. This is most famously illustrated by the 'butterfly effect', which suggests that the tiny disturbances in the air caused by the flapping of an insect's wings might make the difference between a hurricane blowing on the other side of the world or not.
Before this became an established scientific fact, the science fiction writer Ray Bradbury had already described the basic idea in his short story 'A Sound of Thunder', in which a time traveller hunts a Tyrannosaurus rex. On this safari he has to stay on levitating platforms and he is only allowed to kill a dinosaur that was going to die at that precise moment anyway. The time-travel company considers it too risky to kill even the smallest animal that might otherwise have lived. 'For want of ten mice, a fox dies,' explains the guide. 'For want of ten foxes a lion starves.' And then one day a caveman starves because 'you, friend, have stepped on all the tigers in that region. By stepping on one single mouse.' And that caveman could have been the father of a 'race, a people, an entire history of life'. He warns, 'The stomp of your foot, on one mouse, could start an earthquake, the effects of which could shake our earth and destinies down through Time, to their very foundations.' Yet the time traveller is not careful enough, and one butterfly stuck to the bottom of his boot alters the present he returns to.
Chaos theory may or may not be the end of the hope that human beings can ever reliably predict the future on the basis of the laws of physics. But it does not slay Laplace's Demon, since it does not deny that from the very same starting conditions, only one future would follow. Chaos theory simply alerts us to the very big differences small variations can make. This, however, is completely compatible with Laplacian determinism.
The real challenge to determinism comes from quantum physics. The key feature of quantum theory is that it makes certain laws of nature probabilistic rather than deterministic. From a given set of starting conditions, it is not inevitable what will happen next. In quantum physics you cannot tell, for example, whether a radioactive particle will decay or not in the next ten minutes; you can only assign a probability to its doing so. If quantum theory has got this basic claim right, then Laplace's Demon loses his power. He could not predict the future because not everything that happens according to physical laws inevitably happens. Einstein may not have believed it, but God plays dice, so to speak.
But it seems clear to me that the predictability or inevitability of the future is not the real threat to free will that Laplace's thought experiment raises. Take away inevitability from the materialist world view, and you are still left with everything happening as a consequence of matter reacting to matter. The important point is not that everything happens in a way that is absolutely determined. What matters is matter: everything is simply the result of physical events behaving solely according to natural laws, deterministic or not.
The problem therefore is not determinism but what is often called the causal closure of the physical domain. That is, every physical event has a physical cause, and neither quantum physics nor chaos theory changes that. A neuron fires because of another neuron, not because some soul-like ghost in the head tells it to. If you zoom down to the most fundamental levels of physical reality, to atoms and beyond, the behaviour of every particle will be explained by its own nature, the nature of those around it and the laws of physics that govern them. Whether or not this makes every event predictable is beside the point. Whether the laws of physics are ultimately deterministic or whether probability has a role, the only causes of neurons firing are physical causes. And that's what leads people to worry about free will.
So the root of scientific scepticism about free will is not determinism but materialism — the view that everything is constructed from physical matter. 'The kind of threat to our free will might be called a reductionist threat,' is how philosopher Manuel Vargas puts it. 'It is a threat that seems more rooted in our being built up out of smaller "material" things, than it is a fear about determinism, per se.'
In particular, the worry is that what is really driving us is not desire, belief and thought but small physical processes, atoms colliding. Thoughts, beliefs, desires and feelings are just 'epiphenomena': by-products of neural processes that are the real drivers of action. The man who coined the term 'epiphenomenalism' in 1874, T. H. Huxley, compared the belief that conscious thought drives our behaviour with the belief that the whistle on a steam locomotive moves the train. 'The consciousness of brutes would appear to be related to the mechanism of their body simply as a collateral product of its working, and to be as completely without any power of modifying that working as the steam-whistle which accompanies the work of a locomotive engine is without influence upon its machinery.'
A century later, the philosopher John Searle used another vivid metaphor, saying that, according to epiphenomenalists, human beings are like spume on the crest of a wave which thinks 'what a tough job it is pulling these waves up on the beach and then pulling them out again, all day long', and that our mental life is not 'any more important than a froth on the wave of physical reality'. Whichever analogy you prefer, consciousness is just the noise made by the firing of neurons, no more the cause of action than sweat is the cause of a runner's exertion.
That the main threat to free will comes from materialism in general rather than from strict determinism can be seen in Nick Spencer's informative history of atheism, where time and again a denial of free will is part and parcel of the naturalistic world view which led people away from religion. One of the earliest examples of this is Lucretius, who in his first century BCE poem De rerum natura (On the nature of things) describes a universe governed purely by natural laws. In such a world, everything that happens is an effect of prior causes. And so he asked rhetorically, 'if ev'r all motions are co-linked, And from the old ever arise the new ... Whence this free will for creatures o'er the lands, Whence is it wrested from the fates?'
The same basic question again found no satisfactory answer when it was asked by European materialists at the dawn of the Enlightenment. Nature came to be seen as a kind of machine, and so human beings, as parts of nature, became mere cogs within it. Hence Jean Meslier, the eighteenth-century priest thought to be the first avowed atheist, wrote that: 'Man who believes himself free, is a fly who believes himself the master-motor in the machine of the universe, while he himself, without his own volition, is carried on by it.' Similarly, Meslier's compatriot Baron d'Holbach wrote half a century later: 'Is not Nature herself a vast machine, of which the human species is but a very feeble spring?' around the same time as the physician and philosopher Julien Offray de La Mettrie wrote a book called Man a Machine (L'homme Machine).
Time and again, thinkers who have concluded that the universe is governed solely by natural laws have been quick to conclude that there is therefore no space for human freedom. That is the basic inference, and it depends not a jot on determinism, quantum theory or cutting-edge science to make or assess it. The fact that so many scientists appear to think otherwise reveals either philosophical naivety or a cynical exaggeration of the significance of their own research for ordinary life.
Just as the fundamental scientific challenge to free will has been the same for centuries, so the most common strategy to try to respond to it recurs in different guises. This strategy can be understood by analogy to an old problem in theology. Before science began to provide satisfactory accounts of how the universe worked, people would often attribute the workings of nature to God or gods. That is not to say that religion was nothing more than bad proto-science, or that all religions invoked deities in this way. But it would take a breathtakingly modernist rewriting of history to deny that the belief that divine powers directed nature was not extremely widespread.
As science began to mature, it became increasingly obvious that more and more of the workings of the world could be explained by natural laws alone. God seemed to be squeezed out of the picture. As Laplace reputedly said to Napoleon, explaining the absence of God in his account of the celestial movements, 'I have no need of that hypothesis.'
Excerpted from Freedom Regained by Julian Baggini. Copyright © 2015 Julian Baggini. Excerpted by permission of The University of Chicago Press.
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