Book excerpt: Who ought to hold claim to the more dangerous idea--Charles Darwin or C. S. Lewis? Daniel Dennett argued for Darwin in Darwin's Dangerous Idea (Touchstone Books, 1996). In this book Victor Reppert champions C. S. Lewis. Darwinists attempt to use science to show that our world and its inhabitants can be fully explained as the product of a mindless, purposeless system of physics and chemistry. But Lewis claimed in his argument from reason that if such materialism or naturalism were true then scientific reasoning itself could not be trusted. Victor Reppert believes that Lewis's arguments have been too often dismissed. In C. S. Lewis's Dangerous Idea Reppert offers careful, able development of Lewis's thought and demonstrates that the basic thrust of Lewis's argument from reason can bear up under the weight of the most serious philosophical attacks. Charging dismissive critics, Christian and not, with ad hominem arguments, Reppert also revisits the debate and subsequent interaction between Lewis and the philosopher Elizabeth Anscombe. And addressing those who might be afflicted with philosophical snobbery, Reppert demonstrates that Lewis's powerful philosophical instincts perhaps ought to place him among those other thinkers who, by contemporary standards, were also amateurs: Socrates, Plato, Aristotle, Aquinas, Descartes, Spinoza, Locke and Hume. But even more than this, Reppert's work exemplifies the truth that the greatness of Lewis's mind is best measured, not by his ability to do our thinking for us, but by his capacity to provide sound direction for taking our own thought further up and further in.