This article investigates Morgenthau’s views on the ethics of scholarship and argues that all his works should be read in the light of his central goal: speaking truth to power. Doing so demonstrates that for Morgenthau, a realist theory of international politics includes two dimensions: it is supposed to explain international relations, but it is also, fundamentally, a critical project which questions the existing status quo. While the explanatory dimension of realism is debated at great length, its critical dimension is consistently overlooked by the more recent, self-named ‘critical’ approaches which tend to present the two adjectives ‘realist’ and ‘critical’ as mutually exclusive. This amounts to an insidious high-jacking of the very adjective critical, which in most cases merely signals one does not espouse a realist perspective. This is highly problematic as it obscures the fact that for Morgenthau, the founding father of realism, political science is by definition a subversive and revolutionary force critical of the existing order. Highlighting the critical dimension that lies at the core of the realist project as formulated by Morgenthau therefore challenges the current narrow use of the adjective ‘critical’ in the discipline and leads to reclaim it for the realist tradition.