On Saturday John Coatsworth, acting dean of Columbia University's School of International and Public Affairs, made the remark that "if Hitler were in the United States and . . . if he were willing to engage in a debate and a discussion to be challenged by Columbia students and faculty, we would certainly invite him." This was by way of defending the university's decision to host a speech yesterday by Iranian President Mahmoud Ahmadinejad.

An old rule of thumb in debate tournaments is that the first one to say "Hitler" loses. But say what you will about Mr. Coatsworth's comment, it is, at bottom, a philosophical claim: about the purposes of education; about the uses of dialogue; about the obligations of academia; about the boundaries (or absence of boundaries) of modern liberalism and about its conceits. So rather than dismiss the claim out of hand, let's address it in the same philosophical spirit in which it was offered.