The following is based on an essay appearing in Isaiah Berlin: A Celebration, edited by Edna and Avishai Margalit, to be published by the University of Chicago Press.
When Isaiah Berlin delivered his famous inaugural lecture as Chichele Professor of Social and Political Theory at Oxford, in 1958, he felt it necessary to acknowledge that politics did not attract the professional attention of most serious philosophers in Britain and America. They thought philosophy had no place in politics, and vice versa; that political philosophy could be nothing more than a parade of the theorist’s own preferences and allegiances with no supporting arguments of any rigor or respectability. That gloomy picture is unrecognizable now. Political philosophy thrives as a mature industry; it dominates many distinguished philosophy departments and attracts a large share of the best graduate students almost everywhere.
Berlin’s lecture, “Two Concepts of Liberty,” played an important and distinctive role in this renaissance. It provoked immediate, continuing, heated, and mainly illuminating controversy. It became, almost at once, a staple of graduate and undergraduate reading lists, as it still is. Its scope and erudition, its historical sweep and evident contemporary force, its sheer interest, made political ideas suddenly seem exciting and fun. Its main polemical message—that it is fatally dangerous for philosophers to ignore either the complexity or the power of those ideas—was both compelling and overdue. But chiefly, or so I think, its importance lay in the force of its central argument. For though Berlin began by conceding to the disdaining philosophers that political philosophy could not match logic or the philosophy of language as a theater for “radical discoveries,” in which “talent for minute analyses is likely to be rewarded,” he continued by analyzing subtle distinctions that, as it happens, are even more important now, in the Western democracies at least, than when he first called our attention to them.
I must try to describe two central features of his argument, though for reasons of space I shall have to leave out much that is important to them. The first is the celebrated distinction described in the lecture’s title: between two (closely allied) senses of liberty. Negative liberty (as Berlin came later to restate it) means not being obstructed by others in doing one might wish to do. We count some negative liberties—like the freedom to speak our minds without censorship—as very important and others—like driving at very fast speeds—as trivial. But they are both instances of negative freedom, and though a state may be justified in imposing speed limits, for example, on grounds of safety and convenience, that is nevertheless an instance of restricting negative liberty.
Positive liberty, on the other hand, is the power to control or participate in public decisions, including the decision how far to curtail negative liberty. In an ideal democracy—whatever that is—the people govern themselves. Each is master to the same degree, and positive liberty is secured for all.
In his inaugural lecture Berlin described the historical corruption of the idea of…
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