Although Alasdair MacIntyre is best known today as the author of After Virtue (1981), he was, in the 1950s and 1960s, one of the most erudite members of Britain’s Marxist Left: being a militant within, first, the Communist Party, then the New Left, and finally the heterodox Trotskyist International Socialism group. This selection of his essays on Marxism from that period aims to show that his youthful thought profoundly informed his mature ethics, and that, in the wake of the collapse of the state-capitalist regimes in Russia and Eastern Europe, the powerful and optimistic revolutionary Marxist ethics of liberation he articulated in that period is arguably as salient to anti-capitalist activists today as it was half a century ago.