Legal moralism is the view that very nearly all, if not in fact all, the precepts of morality should be enshrined in law.' A factor which obviously militates against this view is that we can be quite mistaken about what morality is, though I have argued that legal moralism is indefensible even if we set aside this difficulty (Thomas 1982). I wish to introduce a somewhat parallel concept, namely biological moralism, which may be understood in the following way. BIOLOGICAL MORALISM. We are products of evolution; and as with rationality, altruistic morality has enormous survival value. Therefore, human beings are naturally moral agents who are disposed to act in accordance with the requirements of altruistic morality, just as human beings are naturally capable of rational thought. So, in the same way that the canons of rationality can be gleaned from the workings of the minds of rational individuals, so can the precepts of morality be gleaned from the hearts and behavior of moral individuals. Indeed, the claim is that by and large we have been stamped by nature as moral beings. Evolution has ensured that the class of individuals in each category would be sufficiently large.