We owe the moral, political and intellectual progress of our species more than anything to individuals whose beliefs or values were sharply at odds with those prevalent at the time. Ockham, Machiavelli, Luther, Giordano Bruno, Galileo, Hobbes, Spinoza, Locke, Hume, Voltaire – these all stand in this tradition, and at the head of it there was, as Mill wrote, ‘a man named Socrates, between whom and the legal authorities and public opinion of his time, there took place a memorable collision’. We remember Socrates as the founder of Western thought; his followers invented the idea of a university. But the upshot of this collision was Socrates’ execution on the charge of ‘corrupting the youth’ of Athens; and it seems that the threat of that charge (though not of that sentence) has revived against modern universities. The effect, predictably enough, is not only a diversion of their resources but an increasing chill on the sort of free and often uncomfortable discussion of ideas that constitutes much of the point of a university.