Nietzsche was a philosopher, not a biologist, Nevertheless his philosophical thought was deeply influenced by ideas emerging from the evolutionary biology of the nineteenth century. His relationship to the Darwinism of his time is difficult to disentangle. It is argued that he was in a sense an unwitting Darwinist. It follows that his philosophical thought is of considerable interest to those concerned to develop an evolutionary biology of mankind. His approach can be likened to that of an extraterrestrial sociobiologist studying (...) clever beasts... in some out of the way corner of the universe ... It is shown how be uses this viewpoint to account for the origin of the central psychobiology of humankind: for dualistic philosophies, such as that of Descartes (which Ryle famously called the official doctrine), for human notions of truth and falsehood, being and becoming, and for other fundamental concepts of Western philosophy and science. All these, he argues, are no more and no less than the necessary adaptations of a zoological species, Homo sapiens, in its struggle for life in a Darwinian world. It is concluded that Nietzsche was the first philosopher to accept and use in their full depth the philosophical implications of nineteeth-century evolutionism, implications which are still resisted to this day. It is also argued that this interpretation of Nietzsche's aphoristic writings provides them with an organic consistency. (shrink)