These exclusive structures can become repressive -- and that repression comes with consequences. In a manner reminiscent of Freud, Mr. Derrida insists that what is repressed does not disappear but always returns to unsettle every construction, no matter how secure it seems. As an Algerian Jew writing in France during the postwar years in the wake of totalitarianism on the right (fascism) as well as the left (Stalinism), Mr. Derrida understood all too well the danger of beliefs and ideologies that divide the world into diametrical opposites: right or left, red or blue, good or evil, for us or against us. He showed how these repressive structures, which grew directly out of the Western intellectual and cultural tradition, threatened to return with devastating consequences. By struggling to find ways to overcome patterns that exclude the differences that make life worth living, he developed a vision that is consistently ethical.

And yet, supporters on the left and critics on the right have misunderstood this vision. Many of Mr. Derrida's most influential followers appropriated his analyses of marginal writers, works and cultures as well as his emphasis on the importance of preserving differences and respecting others to forge an identity politics that divides the world between the very oppositions that it was Mr. Derrida's mission to undo: black and white, men and women, gay and straight. Betraying Mr. Derrida's insights by creating a culture of political correctness, his self-styled supporters fueled the culture wars that have been raging for more than two decades and continue to frame political debate.

To his critics, Mr. Derrida appeared to be a pernicious nihilist who threatened the very foundation of Western society and culture. By insisting that truth and absolute value cannot be known with certainty, his detractors argue, he undercut the very possibility of moral judgment. To follow Mr. Derrida, they maintain, is to start down the slippery slope of skepticism and relativism that inevitably leaves us powerless to act responsibly.

This is an important criticism that requires a careful response. Like Kant, Kierkegaard and Nietzsche, Mr. Derrida does argue that transparent truth and absolute values elude our grasp. This does not mean, however, that we must forsake the cognitive categories and moral principles without which we cannot live: equality and justice, generosity and friendship. Rather, it is necessary to recognize the unavoidable limitations and inherent contradictions in the ideas and norms that guide our actions, and do so in a way that keeps them open to constant questioning and continual revision. There can be no ethical action without critical reflection.

During the last decade of his life, Mr. Derrida became preoccupied with religion and it is in this area that his contribution might well be most significant for our time. He understood that religion is impossible without uncertainty. Whether conceived of as Yahweh, as the father of Jesus Christ, or as Allah, God can never be fully known or adequately represented by imperfect human beings.