"What Happened in the Twentieth Century?: Towards a Critique of Extremist Reason" is a critical exploration of the ideological extremes that characterized the last century. The author examines how political movements, both fascist and communist, shaped the course of history, often leading to catastrophic outcomes. The book delves into the motivations behind these ideologies, highlighting how they exploited societal grievances and pushed for radical change. The text emphasizes the dangers inherent in extremist reasoning, which often dismisses moderation and dialogue in favor of absolute truths. This rigidity can result in intolerance and violence, as seen in numerous historical episodes. The author argues that such extremes are not only results of particular historical contexts but also part of a broader human tendency to simplify complex issues into binary choices.