Why did Kant compare his philosophy to the Copernican revolution?

Immanuel Kant compared his philosophy to the Copernican revolution because he fundamentally inverted the traditional relationship between the human mind and the external world in epistemology.12

Just as Nicolaus Copernicus explained the apparent motions of the stars by attributing them to the movement of the observer rather than the objects themselves, Kant argued that human knowledge is not a passive process of the mind conforming to external things. Instead, he proposed that objects must conform to the mind.13

According to Kant’s transcendental idealism, the mind actively constitutes experience by imposing its own a priori structures—such as the forms of space and time and the categories of the understanding—onto the data provided by sense experience. By demonstrating that the conditions for knowledge are rooted in the knowing subject, Kant shifted the focus of philosophy from describing an independent reality to analyzing the mental framework that makes experience possible.132