Aron begins by defensively insisting to American readers that this topic is still important. But his essays fail to bring the issues to life. They deal with Sartre's Marxism, twentieth-century developments in Marxist thought, and Aron's quarrels with Marxism. The precis of contending positions among what Aron rightly calls the ""para-Marxists"" is inadequate, notably Merleau-Ponty's debates with Sartre. Moreover, Sartre's own progression from existentialism to philosophical anthropology is imperfectly clarified. Nor does Aron exploit the most obviously appropriate approach to the latter--Sartre's effort to fill in missing Marxist theories of ""superstructure."" There are some sound points: the arrested development of Communist thought after 1917 and Sartre's lack of interest in the ""synthetic reconstruction of capitalism"" which preoccupied Marx. But Aron relies on debater's points for intellectual momentum, and depends on one minor writing of Marx's as a primary source. His own comments on political economy are for the most part banal ""age-of-technology"" dicta. At the same time, the book demands more of its audience in the way of philosophical background and acquaintance with the French left than it offers. It combines the defects of both tomes and occasional pieces. Specialists may have already read the essays in French. Thus it seems destined as a small mine for term papers.