Philosophers have not usually looked very kindly on attempts to discuss ethics from a biological perspective. By and large this distaste has been justified by the crudity of many of these attempts. Some good biologists have been poor ethical theorists, failing to distinguish adequately between questions of fact and questions of value. Julian Huxley, for instance, held that evolutionary theory could provide criteria of intrinsic rightness or wrongness, arguing that whether actions are right or wrong depends on their capacity to assist the development of certain types of evolutionary pattern. C.D. Broad pointed out as an "obvious platitude" that to make this work Huxley needed some" 'mixed' premiss, connecting purely factual characteristics, which are all that a study of evolution can possibly reveal to us, with the value-characteristics of instrinsic goodness and badness". 1 But that premiss, said Broad, cannot be derived from evolutionary theory, as "intrinsic value or disvalue" is no part of the subject matter of that theory. Most philosophers have supposed that a criticism of this type can be mounted against any attempts by biologists, whose proper concern is with the realm of fact, to say anything useful, qua biologists, about the realm of value.
But there is a danger of overkill here. It is one thing to say, with Broad, that it is not appropriate to look to biology to provide us with criteria of rightness and wrongness: it is another, and a distinctly more dubious, thing to say that biology is wholly without significant bearing on any interesting features of human moral thought and behaviour. Such overkill, I will argue, mars Thomas Nagel's recent paper "Ethics without Biology"2 This paper forms a convenient focus for my discussion, both because it is a succinct and forceful statement of a position many philosophers lean towards -the position of holding that biology is irrelevant to ethics -and because the problems with that position can be brought out fairly clearly by reference to Nagel's presentation of it.