A comparative study of Kant's theoretical philosophy with Husserlian phenomenology could have been attempted, indeed, should have been attempted, as early as 1913, following the publication of the first volume of Husserl's Ideen zu einer reinen Phänomenologie und phänomenologischen Philosophie—the only volume of the Ideen to appear during Husserl's lifetime. This work, in which Husserl outlines the program of constitutive phenomenology and indicates the general lines along which this program is to be realized, has a clearly Kantian inspiration. Indeed, the first generation of Husserl's students had already perceived this orientation.