Professor Robert P. George is pacing around a Princeton auditorium before 200-plus undergraduates, preparing to wage an intellectual shock-and-awe campaign against illogical thinking. “Some politicians say that they’re ‘personally opposed’ to abortion, yet ‘pro-choice,’” says the 48-year-old professor of constitutional law and moral philosophy. “But we must ask: Is this a position that can survive the test of logical coherence? After all, if abortion is wrong, surely it is wrong because it is the unjust taking of the life of a developing human being.” He pauses to let that sink in and then launches another question: “And if one believes...