Humans are physical beings with evolved brains and evolved minds. Humans are also moral agents with consciousness and will. How should we try to reconcile these very different visions of our humanness? Is it possible - or even desirable - to attempt such a reconciliation? Much of the spit and fury of recent debates about what science can and cannot tell us about human nature has emerged from attempts to answer these questions.
For some, the 'dual character' of human nature is a scientific embarrassment that can only be resolved by viewing consciousness and agency as fictions. The philosopher Derk Pereboom, for instance, in his recent book Living Without Free Will, argues that 'given our best scientific theories, factors beyond our control ultimately produce all our actions, and we are therefore not morally responsible for them.'
Others argue that if scientific advances threaten to undermine our concept of morality, then science itself will have to be reined in. The novelist Tom Wolfe worries that 'science has stolen our soul' while Francis Fukuyama wants tighter regulation on genetics and neuroscience, fearing that they are undermining fundamental human values, including our concepts of moral responsibility and legal rights. Such critics view free will and morality as mysterious phenomena not amenable to rational inquiry and seek to protect the 'human realm' from the clutches of science.
The philosopher Daniel Dennett has long been a champion of the materialist view. Humans, he believes, are evolved machines. There is nothing more to the mind than the workings of the brain. But he also regards free will as real and important. 'Human freedom', he writes, 'is not an illusion; it is an objective phenomenon, distinct from all other biological conditions and found in only one species, us.' Since human freedom is real, 'so it can be studied objectively from a no-nonsense, scientific point of view.' And in Freedom Evolves, Dennett attempts to produce just such no-nonsense, scientific account of human freedom, to reconcile the seemingly irreconcilable.
Reading Dennett is a bit like watching a high-wire trapeze artist. You're forever on the edge of your seat, marvelling at the dextrousness of the amazing moves, but constantly fearing that he's about to fall off. It's exhilarating, but exhausting - as the best writing should be.
The conventional arguments against both free will, on the one hand, and scientific materialism, on the other, rests on the belief that in a deterministic universe there is simply no room for freedom. If every state of the universe has been determined by a previous state then in what way could any act be said to be 'free'? Is it not simply the inevitable outcome of a series of causal links that goes all the way back to the Big Bang?
Not so, says Dennett. Such a view confuses determinism and inevitability. Suppose I'm playing baseball and the pitcher chucks the ball directly at my face. I turn my head to avoid it. There was, therefore, nothing inevitable about the ball hitting my face. But, a sceptic might say, I turned my head not of my own free will but was caused to do so by factors byond my control. That is to misunderstand the nature of causation, Dennett retorts. What really caused me to turn my head was not a set of deterministic links cascading back to the beginnings of the universe - though that certainly exists - but my desire at that moment not to get hit by the baseball. At a different moment I might decide to take a hit in the face, if by doing so I help my team win the game.
How you respond to such arguments depends, I suspect, on what you already believe in. If, like me, you accept that freedom and determinism are compatible, you applaud Dennett the trapeze artist performing a miraculous feat on the high wire. If, on the other hand, you think that the coexistence of freedom and determinism is a preposterous notion, you probably saw him fall off a long time ago.
Having established that a deterministic universe still leaves room for free will, Dennett then attempts to show how such freedom could have evolved just like any biological structure, such as a heart or an eye. Natural selection, he argues, designs organisms that are increasingly able to control their environments. And as organisms become behaviourally more complex, this includes not just the outer environment but also the inner environment of brain and mind.
Understanding one's own mind becomes particularly important in humans with the development of language. As humans begin communicating with others, so they require better understanding of themselves and their own minds. So, evolution designs new ways of monitoring our own thoughts and of keeping track of them. Such access to our thinking is what we experience as 'consciousness'.
Where does free will fit into all this? For most people, conscious will derives from what they would call the 'self'. But this notion of the self, according to Dennett, is an illusion. The self is not the entity that governs brain processes, but is the outcome of those processes. Echoing the neurologist Daniel Wegner, Dennett suggests that 'People become what they think they are, or what they find others think they are.' Free will, in other words, is not the capacity to do something but the capacity to know that something is being done in your name. Dennett has reconciled the seemingly irreconcilable effectively by redefining freedom out of existence.
The real difficulty with Dennett's argument is not his belief that freedom and determinism must coexist - a proposition with which I agree - but his insistence on viewing agency simply as a biological phenomenon. Our very possession of agency reveals that humans cannot be understood in this fashion. Agency is an expression not just of our embodiment in nature but also of our capacity to transcend it. It is an expression of our existence not simply as natural creatures but also as historical beings.
All animals have an evolutionary past. Only humans make history. And it is through history that freedom develops. Our Stone Age ancestors were biologically identical to us, but they could not be free in any real sense because they were almost completely at the mercy of natural forces. The development of consciousness, and hence of freedom, requires humans, through historical progress, to begin to control nature and to regulate its impact upon our lives.
Natural science, in other words, can tell us much about humans as natural beings. But it is limited in what it can say about humans as moral agents. Not because agency is mysterious and beyond rational ken, but because it is a product of history and politics, not of nature.
There is an unwitting thread that links Dennett's argument to that of critics such as Tom Wolfe or Francis Fukuyama. Dennett believes that 'science can help put our moral lives on a new and better foundation'. The critics worry that science might undermine our moral lives altogether. The real problem is that both sides have turned science into the battleground for what are essentially political and moral debates. Science will not undermine human freedom. But nor will it necessarily bolster it. Freedom is a political, not a scientific, issue.