What is Open Marxism? Against a background of social regression and the ongoing, multifaceted crisis of capitalism, this book examines the Open Marxist tradition and how it develops the work of the early Frankfurt School in ways which significantly advance critical social theory as negative critique of capitalist society. The study situates Open Marxism as the latest critique of mechanistic interpretations of Marx and Marxism, evolutionism and positivism, and ‘’naturalized’’ historical and societal processes. It charts the development of the different strands of Open Marxism: from Axelos in the 1950s, and Agnoli in the 1980s, to the work of Clarke, Bonefeld, Gunn and Holloway since the 1990s. The book describes the distinctive features of Open Marxist thought with a focus on its use and understanding of critique as negative and destructive. Negative critical theory is argued to be the only path still open to the possibility of human emancipation, and this volume describes how Open Marxism can be put to use in the work of building radical social praxis, with reference made in particular to the critique of class, political economy and the capitalist state. Explaining how Open Marxism’s subversive negation of capitalist social relations and radical critique of capitalism’s various perverted social forms this book is a vital contribution to a body of Marxist thought concerned with the contemporary struggle for human emancipation.