There is a notion, cataleptic in its effects, that discussion in ethics and values must ultimately be blocked by the “naturalistic fallacy.” We can go so far in analyzing the categories of “good,” “right,” “ought,” “valuable,” and the like, but never so far as to embark from the field of logic or general philosophy and enter the alien provinces of science—at least with a visa. To think to reduce moral problems to those of psychology or biology or (in Northrop's amendment) to those of “culture,” is The Fallacy, insensitivity to which brands one as a positivist, a dupe of “scientism,” or at least a sympathetic fellow-traveller. Though the vocabulary of The Fallacy is not old—G. E. Moore and his earnest commentators will date it—the idea is almost as antique as philosophy itself; indeed, it is one of the prime devices whereby philosophy has managed to rationalize its subject-matter as something more than an historical accident.