In this analysis of the problem of freedom from a humanistic-Marxist perspective, philosopher Kevin M. Brien draws on the full chronological spectrum of Marx's writings to reconstruct the mature Marx's view of freedom under three broad categories: freedom as a mode of being, freedom as transcendence, and freedom as spontaneity. While recognizing that many students of Marx have noted two distinctly different perspectives in early and late Marx, Brien interprets Marx's philosophy as a coherent organic whole. He demonstrates that Marx's thought is principally and systematically an elaborated philosophical-scientific theory of freedom. New to this second edition is an extended postscript in which Brien provides critical responses to a number of published reviews of the first edition of his book. In addition, Brien also presents a humanistic-Marxist interpretation of spirituality. In so doing he identifies a potential revolutionizing agency in the context of the 21st century. Finally, an addendum shows how humanistic Marxism and Buddhism converge on the same basic values and mutually complement each other. This comparison serves to emphasize the viability of projecting a nontheistic spiritual dimension and shows that there is a genuine moral basis for common social action among adherents of different perspectives. This rigorously argued and deeply thoughtful analysis reveals the continuing relevance and promise of Marx's thought in the 21st century.