This paper delves into Michel Foucault’s critical examination of Immanuel Kant’s philosophy of enlightenment, primarily through Foucault’s essay What is Enlightenment? It summarizes Kant’s conception of enlightenment as the liberation from self-imposed immaturity through the courageous use of reason, and highlights Kant’s distinction between public and private reason. Foucault critically assesses Kant’s views, questioning the universality of enlightenment and the dichotomy between public and private reason. By integrating insights from Charles Baudelaire on modernity, Foucault reframes enlightenment as a critical spirit intrinsic to modernity, emphasizing perpetual questioning, innovation, and identity formation. The paper concludes that Foucault’s critical ethos advocates for an ongoing, radical examination of enlightenment and rationality, safeguarding against complacency and fostering independent thought.