Why we need a materialist spirituality for the secular left, and how to build one. The left commonly rejects religion and spirituality as counter-revolutionary forces, citing Marx's famous dictum that "religion is the opium of the people." Yet forms of spirituality have motivated struggles throughout history, ranging from medieval peasant uprisings and colonial slave revolts, to South American liberation theology and the US civil rights movement. And in a world where religion is growing, and political movements are ridden with conflict, burnout, and failure, what can the left learn from religion? Red Enlightenment argues not only for a deepened understanding of religious matters, but calls for the secular left to develop its own spiritual perspectives. It proposes a materialist spirituality built from socialist and scientific sources, finding points of contact with the global history of philosophy and religion. From cybernetics to liberation theology, from ancient Indian and Chinese philosophy to Marxist dialectical materialism, from traditional religious practices to contemporary art, music, and film, Red Enlightenment sets out a plausible secular spirituality, a new socialist praxis, and a utopian vision.