Image by Martin Trefzer
In any respectable university bookshop it’s increasingly common to find books on Darwin nestling on the ‘philosophy’ shelves. But what makes Darwin a philosopher? Of course, in his time there wasn’t quite today’s distinction between ‘natural philosophers’ (scientists) and ‘moral philosophers’ (us lot). But why should we find him of philosophical interest now?
There are a couple of reasons: first is the impact of Darwin’s theory of evolution by natural selection on our view of ourselves and of our place in the universe, and on certain traditional philosophical arguments which prior to Darwin might have seemed conclusive.
The second is the continuing importance of Darwin to debates in the philosophy of science, and specifically the philosophy of biology, but I’m not going to say any more about these.
Let’s begin with a sketch of what the theory of natural selection actually claims.
Why do living creatures take the form they do; why are creatures so well adapted to a particular way of life? A familiar pre-Darwinian answer is that they have been designed for that way of life; that their particular form is the result of a pre-existing blueprint which expresses the purpose of a designer.
The most famous expression of this idea is in William Paley’s Natural Theology. If we came across a watch on the heath, says Paley, we could tell from the way in which the parts worked together to fulfil a purpose (telling the time) that it had been designed for that purpose. And
… every indication of contrivance, every manifestation of design which existed in the watch, exists in the works of nature’ (Paley, Natural Theology 1802)
The natural world demonstrates the same appearance of design as the watch, and Paley argues that this must mean that it is designed. An account like Paley’s is teleological; it thinks of the natural world in terms of purpose, of things existing to fulfil certain goals.
Natural selection provides a quite different sort of answer. It proposes that creatures take the shape they do as a result of a combination of natural causes. Since
- There is competition between creatures for resources; and
- Genetic variation occurs, leading to offspring sometimes having slightly different features from their parents; and
- Some of these features will benefit a creature in the competition for resources; and
- These features can in turn be passed on to the next generation
… we should expect creatures to come to differ from one another over time and eventually to make up different species. The unsuccessful variants don’t compete as well, produce fewer offspring and eventually die out, and the successful ones become increasingly specialised to life in their particular environment.
This is a non-teleological account. Creatures are not made to fit their environment; instead, only those fit for the environment survive.
The Darwinian answer to a question like ‘why do giraffes have long necks?’ is not ‘so that they can eat the leaves off high trees’ but ‘all those without long necks died out, because they lost the battle for resources’. Janet Radcliffe Richards puts it nicely; teleological answers pull from in front (they always have some purpose or aim in mind), while non-teleological answers push from behind (they focus on causes, not aims).
Notice four things. First, this account tells us nothing about the origins of life; how cells capable of genetically guided replication initially came into existence.
Second, this is not a chance process (although perhaps genetic variation is, to all intents and purposes, chance). Given the four initial conditions above and enough time, change and adaptation is inevitable. Natural selection is causal, mechanical, algorithmic.
But—third—it is not a sort of design process either. Natural selection does not design creatures. There are all sorts of possible solutions to the problem of existence, and these solutions need not be perfect, merely good enough to outstrip the competition. So we might expect to find—as we do—that animals have certain features that appear superfluous, or that don’t work very well.
Finally notice that this is not, taken as a whole, a process of progressive improvement. While one variant creature may be better than another at surviving and reproducing there is no sense in which the whole process produces ever better and better creatures. ‘Better’ just means better at surviving and reproducing; a sponge is as good as a gorilla in that respect (perhaps superior, since sponges have been around for longer), and natural selection provides no grounds for thinking of humankind as somehow nature’s final word. Time will tell.
This is what causes much of the trouble. If we accept natural selection, how should we think of ourselves? This question becomes particularly acute when we ask whether human nature is a product of natural selection. Perhaps we share behavioural tendencies and basic values only because these support survival and reproduction. If so, should this diminish our respect for morality, society and human virtue? As Dan Dennett puts it, Darwinism might seem to be a ‘universal acid’, attacking our view of ourselves and our most cherished values.
I agree with those philosophers who say that in this respect, Darwinism changes very little. If it leads us to have a little more humility towards the rest of the natural world that may be no bad thing. But our judgements about what is of value are not altered by claims about the origins of those judgements. If something was valuable to us before Darwin, it remains of value afterwards.
The rest of the trouble tends to be caused by the implications of Darwinism for religious belief (there are connections between these two issues, of course). We’ve already seen how Darwinism is non-teleological, providing an economical account of design-like features that does not require a designer.
But we must be clear about what such an account shows. It doesn’t disprove the existence of God. Nor, in fact, does it demonstrate that there cannot be a designer; natural selection may still be a designer’s preferred means to achieve their end. As Anthony Kenny puts it ‘a system may operate teleologically while being mechanistic in structure’.
But by providing an alternative explanation for design-like features of the natural world, natural selection reduces their value as evidence for a designer. And more generally, by providing an account of how apparent purpose can emerge from mechanistic natural forces, it provides support for an account of the world in terms of natural processes alone.
Nick Jones is a teaching fellow in the Philosophy Department at the University of York
 Natural selection was proposed independently by Alfred Russell Wallace, an interesting character in his own right. It was a letter from Wallace that provoked Darwin into publishing the work he had been engaged in for some years.