[P]olitical philosophy must be realist. That means, roughly speaking, that it must start from and be concerned in the first instance not with how people ought ideally (or ought “rationally”) to act, what they ought to desire, or value, the kind of people they ought to be, etc., but, rather, with the way the social, economic, political, etc., institutions actually operate in some society at some given time, and what really does move human beings to act in given circumstances. The emphasis on real motivation does not require that one deny that humans have an imaginative life that is important to them, aspirations, ideals they wish to pursue, or even moral views that influence their behaviour. It also does not imply that humans are not sometimes “rational,” or that it would not often be of great benefit to them to be “rational.” What it does mean, to put it tautologically, is that these ideals and aspirations influence their behaviour and hence are politically relevant, only to the extent to which they do actually influence behaviour in some way. Just because certain ideal or moral principles “look good” or “seem plausible” to us, to those who propose them or to those to whom they are proposed—to the prophet or to the people whom the prophet addresses—it does not follow that these norms, canons, or principles will have any particular effect at all on how people will really act. Even if one were to assume something I am loath to admit, namely, that certain moral principles that have determinate content are “absolutely true” or “eternally valid” or could be “ultimately justified by reference to the nature of reason itself,” this would not automatically ensure that these principles were in fact universally recognised—what truths except utterly trivial and banal ones are “universally” recognised? It would also not ensure that, even if they were recognised, they would be universally obeyed. Finally, a political philosopher cannot take ideals, models for behaviour, or utopian conceptions at their own face value. That the prophet claims and genuinely believes that his table of values will bring peace and prosperity to his followers, and even that the followers genuinely believe this and act according to the table of values to the best of their ability, does not ensure that peace and prosperity will in fact follow. Even if the population did prosper, that would not, in itself, show that the prophet had been right. This could just have been luck, or the result of completely different factors. A realist can fully admit that products of the human imagination are very important in human life, provided he or she keeps a keen and unwavering eye upon the basic motto Respice finem, meaning in this case not “The best way to live is to keep your mind on your end: death,” but “Don’t look just at what they say, think, believe, but at what they actually do, and what actually happens as a result.” An imagined threat might be an extremely powerful motivation to action, and an aspiration, even if built on fantasy, is not nothing, provided it really moves people to action. This does not mean that it is any less important to distinguish between a correct perception of the world and illusion. The opposite of reality or the correct perception of reality is in any case not the imagination but illusion; however, even illusions can have effects. The realist must take powerful illusions seriously as factors in the world that have whatever motivational power they in fact have for the population in question, that is, as something to be understood. This is compatible with seeing through them, and refusing steadfastly to make them part of the cognitive apparatus one employs oneself to try to make sense of the world. It is no sign of gimlet-eyed realism to deny the enormous real significance of religious practices, beliefs, and institutions in the world, past and present, but, rather, a sign of simple blindness. This, however, does not imply that the cognitive or normative claims made by religious believers have any plausibility whatever.

(Raymond Geuss, Philosophy and Real Politics [Princeton and Oxford: Princeton University Press, 2008], 9-11 [italics in original; endnote omitted])

Note from KBJ: The key sentence in this passage is this:

The realist must take powerful illusions seriously as factors in the world that have whatever motivational power they in fact have for the population in question, that is, as something to be understood.

Does Professor Geuss think that only ordinary people, i.e., nonintellectuals, labor under illusions? (Recall Barack Obama's quip about the people of Pennsylvania "cling[ing] to their guns or religion or antipathy toward people who aren't like them.") What about the Marxist illusion of class conflict? What about the progressive illusion of the blank slate? What about the feminist illusion of the indistinguishability of the sexes? What about the egalitarian illusion that there are no races? Do intellectuals such as Professor Geuss see through their own illusions? If not, then they are in no better shape than the ordinary people on whom they look down.