My topic may seem a bizarre mixture of epistemology and value theory; and perhaps it is best to acknowledge this oddity at once. I should also, perhaps, confess that such a mixture has always seemed something to aspire to. Any philosopher who has made it seem that feeling strongly about something, valuing it highly, is an inevitable consequence of the nature of human understanding, that from the facts of knowledge or perception one can derive the inescapable facts of emotion or desire, any such philosopher has always deeply appealed to me. I am therefore a confessed perpetrator of the naturalistic fallacy. Indeed I go further, and say that I love the fallacy. So Spinoza, Hume (however much people say that he first discovered naturalism to be fallacious) and Sartre all seem to me to be real philosophers, on the grounds that for them this connexion between knowing and wanting seemed inevitable. My aim is to illustrate this kind of connexion by suggesting that the human imagination is such that we ought to value it and respect it more highly than anything else; and that therefore, if it can be educated and improved, it is to this education that we should give priority, if we are concerned with education at all. It may seem on the face of it absurd to say that we ought to value any particular human faculty or capacity. It may be thought that this is not the kind of object or evaluation with which at any rate philosophers should be concerned. But the fact is, of course, that we do value very highly indeed all kinds of capacities that we have, such as sight, and hearing and understanding. And being unashamedly naturalistic, I have no hesitation in saying not only that we do value them, but that we ought to; they are, in every sense, valuable.