A preliminary modesty becomes a new professor; and a deprecatory preface to his inaugural discourse is not only a decency, but also a debt, when the new professor is sitting uneasily in a new chair to expound a subject which, he well knows, many of his hearers will regard as certainly nebulous, probably dubious, and possibly disputatious. Happy is the Cambridge man, with history bred in his very bones, who returns to Cambridge, after years of devotion and service, to declare the ascertained mysteries of the muse Clio;1 but unhappy, thrice unhappy, is the Oxford man, who comes to Cambridge for the first time, dripping from seven years of immersion in the bewildering complications of the University of London, to profess an uncertain subject about which he has already forgotten more than he ever knew. To come to Cambridge-the home of exact knowledge, where men walk on the razor’s edge of acute analysis-and to come, with such an equipment, for the exposition of such a subject, is a bold and desperate thing. I can only promise, as I do with a genuine sincerity, to attempt to ascertain the nature of my subject: to seek to discover the facts, if such there be, which form its basis; and to try to analyse, as best I can, their significance and implications. And I may perhaps be allowed to take some measure of comfort from the reflection that such experience of affairs as I have had in London during the last seven years may give to my lectures that tang of reality which my subject especially needs. No philosophy of human life can live by books alone; and political philosophy, no less than other forms, must study the busy hum of affairs in the cave before it can move into the upper light of contemplation.