The diagnosis of the sources of the illusion is that the rational psychologist, the Cartesian philosopher of the soul, confuses the unity of experiences with the experience of unity. The rational psychologist maintains that every man has immediate assurance of the existence of his own soul as immaterial substance, identical throughout the succession of its states. From the incoherence into which David Hume's theory of the self thus lapses, and of which he himself was not unaware, Immanuel Kant's exposure of the illusion of rational psychology is altogether free. Kant goes much further, in accordance with the demands of the disastrous model whose sources people have not yet fully explored. To Kant himself, however, the commitment to transcendental idealism seemed to make the exposure of the illusion a matter of particular urgency. The title of "transcendentalism" might indeed be justified by the doctrine that all that people know in experience is dependent upon some unknown ground inaccessible to experience.