JOHN Gray is one of Britain’s most publicly engaged, pro- vocative, and prolific political thinkers. Over the past two decades he has written or edited over a dozen books, including expositions of his own thought and studies of such thinkers as John Stuart Mill, Voltaire, Friedrich Hayek, and Isaiah Berlin.  He has become, in turn, a Thatcherite, a critic of Thatcherism from both the traditional Right and the environmentalist Left, and an early supporter of Tony Blair and New Labour. By his own account, his theoretical position has shifted almost as much as his politics. Yet liberalism, in the broadest sense of the term, has remained the focus of his thinking.