Particular Reasons

According to contemporary physics, there are four fundamental forces: the strong nuclear, weak nuclear, electromagnetic, and gravitational. One of the greatest successes of twentieth-century physics was the realization that the electromagnetic and weak nuclear forces could be unified into one—that they could be understood as two aspects of a single electroweak force. This discovery led to attempts at formulating a ‘grand unified theory’, as it came to be called, that would unify the three forces other than gravity. And now the search is on for an even more ambitious theory, a so-called theory of everything uniting all four fundamental forces. Perhaps some version of string theory will produce such a theory; perhaps some other, as yet unthought of theory will do the trick. But although progress has been hampered by our current lack of experimental evidence for the hypotheses being proposed, most practicing physicists are confident that a unified theory of the four fundamental forces is out there to be found. There is a long-standing tradition in ethics with similar aspirations. On this approach, ethics is seen as involving a search for a grand unified theory of the moral realm, a quest for a “supreme principle of morality” (as Kant called it) that would constitute a theory of everything with respect to right and wrong. This single, universal principle could then be used to discover which of the actions available to us in a given circumstance are right and which are wrong and also to justify (both to ourselves and to others) why, exactly, the right actions are right and the wrong ones are wrong. The two best-known attempts at such a