Roberto Mangabeira Unger (b. 1947, Rio de Janeiro) is a Brazilian contemporary social theorist, politician, and law professor at Harvard Law School.

He is the Harvard Law School's only South American faculty member. He was associated with the Critical Legal Studies movement for a brief period in the late 1970s and early 1980s, although Unger has set forth his own criticisms of some of the central ideas that emerged out of this movement, in particular the indeterminacy debate in legal theory, which Unger calls the "radicalization of indeterminacy" in his own writings. He also taught Barack Obama while in Harvard.

This manifesto develops the major ideas of an intellectual movement that has transformed traditional views of law and legal doctrine. The book also provides an introduction to Unger's social theory, a radical alternative to Marxism.

Critical legal studies has shown how the conflict over basic social arrangements and social visions, which seems relegated to philosophy and revolutionary politics, reappears in the subtle disharmonies of the law and the daily practice of legal analysis. The law juxtaposes, and fails to reconcile, countless small-scale variations in our ways of imagining and organizing governments, economies, and families. By facing the need to choose among such alternatives, we rediscover more fundamental challenges to the established social order. Unger's remorseless development of this theme is a model of constructive dissidence and radicalism. It will be of interest to political activists as well as to scholars in all fields of social, historical, and literary studies.

The Critical Legal Studies Movement introduces the reader to the central concern of Unger's recent work in social theory: the revision of the modernist image of personality, the search for an antinecessitarian view of social life, and the invention of governmental and economic arrangements that advance the cause liberals and socialists share.