Sophia at the Beach.

A Refutation of Moral Relativism: Interviews with an Absolutist, by Peter Kreeft (Ignatius, 177 pp., $12.95)

IN Plato's Athens, the practice of writing was just becoming widespread (his teacher Socrates never wrote anything), so philosophy, that favorite Athenian pastime, was usually done through conversations rather than in treatises. Plato held the common belief that philosophy lost something when written down, but realized that it was lost for good unless committed to paper. His solution was to compose philosophical dialogues, hoping that by dramatically presenting a many-sided argument he could seduce the reader into wrestling with the issues just as if he himself were engaged in the discussion.

Ever since Plato invented and mastered the genre, philosophers from time to time have returned to it as a way of doing philosophy in public. Peter Kreeft of Boston College has a real talent for this type of writing, as his earlier dialogues on abortion (The Unaborted Socrates) and the meaning of success (The Best Things in Life) amply revealed. In his latest book, Kreeft takes on moral relativism--the idea that what is right and what is wrong differs from culture to culture, from era to era, from person to person.

He sets the dialogue at his own summer house on Martha's Vineyard, where the fictional Kreeft invites two former students for a week of sun, surf, and sophia. The arrangement is for Liberty ("Libby") Rawls, a black feminist journalist, to record an interview with 'Isa Ben Adam, a Muslim philosophy professor who makes the case for truth. Kreeft makes no pretense that the journalist can match the professor in philosophical discourse: Like Socrates in Plato's dialogues, 'Isa (Arabic for "Jesus") is clearly in control. Nevertheless, the sassy, honest Libby--the voice of experience rather than theory--steals the show. She is a more likable character than the know-it-all absolutist, so even when 'Isa wins the argument, he comes off seeming smug and a little impolite (like many a real-life absolutist). As a result, you can give this book to your relativist friends, and they won't think Kreeft shortchanges their side.

For that matter, 'Isa's arguments are not as strong as he seems to think they are. Now, in real life it would be a disaster to claim to refute moral relativism and then not do it well, since one would thereby make the weaker intellectual position look strong (as the sophists accused Socrates of doing). But in the context of a dialogue, having the smug character present a less than airtight argument is highly seductive. The relativist will find here arguments good enough that he can take them seriously, but weak enough that he is encouraged to refute them, changing in the process from a spectator to a participant. Therein lies Kreeft's artfulness: Once a moral relativist starts to think hard about relativism, he's a goner. For the moral relativism of our culture is unreflective, and cannot withstand much scrutiny. As Prof. Kreeft clearly realizes, the more we trick relativists into thinking about their beliefs, the better it is for Western civilization.

Mr. Moloney is associate editor of First Things.