In his 1908 masterpiece Orthodoxy, G. K. Chesterton explored the phenomenon of modern theologians who deny the reality of sin. "The strongest saints and the strongest skeptics alike took positive evil as the starting point of their argument," Chesterton wrote. "If it be true (as it certainly is) that a man can feel exquisite happiness skinning a cat, then the religious philosopher can make one or two deductions. He must either deny the existence of God, as all atheists do; or he must deny the present union between God and man, as all Christians do. The new theologians seem to think it a highly rationalistic solution to deny the cat."

There are no cats in The Conservative Soul, the new book by Andrew Sullivan. There is, however, tautology, narcissism, and enough moral relativism to light Manhattan for ten years. Sullivan's premise is simple: We just can't know anything for sure. There's no real truth, and anyone who claims otherwise is not really a conservative but rather a fundamentalist. "The essential claim of the fundamentalist is that he knows the truth," Sullivan writes. "The fundamentalist doesn't guess or argue or wonder or question. He doesn't have to. He knows." In opposition stands the true conservative, whose "defining characteristic" is that "he knows he doesn't know."

The true conservative's only guide, posits Sullivan, is his conscience. The conscience is protean and, in Sullivan's case, prone to New Age bromides: "As humans, we can merely sense the existence of a higher truth, a greater coherence than ourselves; but we cannot see it face to face." According to Sullivan, "We see the world from where we are, and our understanding of the universe is intrinsically rooted in time and place. We can do all we can to ...