During the second half of the 19th century, the First International of Workers was shaken and split by the relentless conflict between Mikhail Bakunin and Karl Marx, these emblematic figures who led the two competing tendencies within the revolutionary and socialist movements of the time. The former represented the libertarian, anti-authoritarian, anarchist current, while the latter represented authoritarian "scientific" socialism and state communism. The tragic 20th century, the century of extremes, with the barbarity of its various totalitarianisms, came to confirm, in the most painful way, Bakunin's critical observations and predictions about statism, centralism, hierarchical mechanisms, bureaucracy, technocracy, as well as the transformation of revolutionary vanguards into a new class of ruthless oppressors. The texts in this volume, written by libertarian thinkers, deep connoisseurs of Bakunin's work as well as Marxism, present the ideas and radical critique that this passionate lover of freedom exercised on Marx's authoritarian scientism, regarding political philosophy, economics, and, above all, politics.