W 'hen surveys of faculty tell us that politically right-of-center voices are now much reduced or even in certain areas largely absent, we can be sure that the academy is damaged in at least one respect: the campus political and social climate will be unrealistic. 1 Programs where this is central, such as political science and sociology, will be damaged most, but its effect will be felt throughout the humanities and the social sciences. That's bad enough in itself. But the kind of damage I want to talk about goes deeper than this--and that is the damage done more generally to the quality of teaching and research when the campus is so politically one-sided. Students go to college to learn to think in a disciplined way: how to shape arguments and recognize weak ones, how to marshal evidence, how to analyze issues and draw valid conclusions. All of that requires that they develop an intellectual curiosity that is not limited by their own, or anyone else's preconceived opinions. Giving students this kind of education is a core function of the university. If the campus political monoculture damages this--as I think it does-that is infinitely more important than the narrower question of a realistic political climate. Defenders of the academy as it now is tell us that the political tilt makes no difference to teaching and research, because the campus has always leaned left, and because professors are professionals who teach their subjects conscientiously whatever their politics. And once they take that position, these defenders must regard the campus horror stories of unprofessional, politically motivated behavior that we hear so often as atypical, isolated cases without wider significance. 2 This defense is certainly not a good example of disciplined thinking. First of all, just the way in which political one-sidedness is distributed tells us that it has not always been as it is now. It is very much more pronounced among younger faculty than among older faculty, which shows both that it used to be less extreme than it is now, and also that it is getting worse all the time, as older faculty retire and are replaced by younger ones. The distribution by department also tells us that things are not as they once were. A recent survey of faculty political registrations in major universities found that in some departments of political science (of all places) there were no professors registered as Republicans, while dozens were registered to parties