In Western thought, it is often observed, the idea of nature has played a role that has been both fundamental and ever-changing. Three main stages in its development can perhaps be retrospectively identified. They are distinct from one another, of course, only as ideal types; historically speaking they overlap, and even the earliest of them continues to inform our thinking. But as ideal types, each can be seen as a reaction to the previous one.

The first is of nature as essentially harmonious. Human beings are at home in the world, and there is a cosmic order that is not physical but ethical. Reality is divinized. This broad framework has been compatible with a number of different stages of historical development. It seems characteristic of pre-historic peoples, of early civilizations, and even (to some extent) of the medieval period in the West. It is possibly (as Donald Brown has remarked) part of a universal phenomenology of human consciousness; that is, it applies to all human groups in their first formation. Even societies like the Inca who perceived their gods as in some sense threatening and demanding of human sacrifice can be said to conform to the pattern - they have only inverted the valuation of being in the world that is involved.

The second phase is a reaction to this one. In it, human beings are no longer in harmony with nature or one another, but must struggle to survive. Existence is a competitive affair. Perhaps the origins of this view, so far as the West is concerned, are Hebraic - the idea of the Fall and the casting out of man from paradise; though the Greeks too thought in terms of a lost golden age. Christianity took up this idea of the fallen condition of humanity, which is why the medieval (and even the ancient) notion of man as in harmony with nature was always qualified. But it is from the seventeenth century onwards that this idea of the state of nature as competitive develops. Hobbes is a central figure here. In the nineteenth century Darwin arrives at the view that nature itself and not merely the human place in it has competition as its fundamental feature.

The third phase is the attempted abolition of nature as a concept altogether. Human 'nature' is conceived of as entirely plastic. To some extent this phase too overlaps with the second; it is also characteristic of the Renaissance, and is articulated by Mirandola, for example. But it remains overshadowed by the idea there being a fixed order of some kind as defined by both of the first two phases until the later nineteenth century. Marx represents it only ambiguously, as he retains the idea of an unalienated nature in the concept of 'species being'. It is found more clearly in anthropology and psychology, in which culture and mind are empty categories waiting to be filled. Locke, from this perspective, is caught between the second and third phases of this movement. But for most of the twentieth century it was thought that with a sufficient effort of will, people could be made in whatever image one desired; this is one important root, though by no means the only one, of the ideological experiments that caused so much destruction.

The fourth and final phase is only just beginning; it is a product of the late twentieth century. It is the reassertion of a concept of human nature, but on the basis of empirical and historical evidence. Human beings turn out, on inspection, to have a great deal in common with one another; at least as much as what divides them. The reassertion of the idea that there are human universals has been prompted partly by reflection, and partly by circumstances; Foucault and many others are correct in pointing out that our continued survival as a species is now intimately bound up with our choice of political strategies thanks both to the awesome destructiveness of our weapons and our continued economic exploitation of our environment. But a common human identity which transcends national divisions is politically essential if we are to ensure a peaceful and prosperous future for ourselves.