By the end of the twentieth century, it had been almost forgotten that the Freudian account of the unconscious was only one of many to have emerged from the intellectual ferment of the second half of the 19th century. The philosophical roots of the concept of the unconscious in Leibniz, Kant, Schelling and Schopenhauer had also been occluded from view by the dominance of Freudianism. From his earliest work of the 1940s, until his final writings of the 1990s, Gilles Deleuze stood at odds with this dominant current, rejecting Freud as sole source for ideas about the unconscious. This most 'contemporary' of French philosophers acted as custodian of all the ideas that had been rejected by the proponents of the psychoanalytic model, carefully preserving them and, when possible, injecting them with new life. In 1950s and 60s Deleuze turned to Henri Bergson's theories of memory and instinct and to Carl Jung's theory of archetypes. In "Difference and Repetition (1968)" he conceived of a 'differential unconscious' based on Leibnizian principles. He was also immersed from the beginning in esoteric and occult ideas about the nature of the mind. "Deleuze and the Unconscious" shows how these tendencies combine in Deleuze's work to engender a wholly new approach to the unconscious, for which active relations to the unconscious are just as important as the better known pathologies of neurosis and psychosis.

One of the terminological constants in the philosophical work of Gilles Deleuze is the word 'immanence', and it has therefore become a foothold for those wishing to understand exactly what 'Deleuzian philosophy' is. Deleuze's philosophy of immanence is held to be fundamentally characterised by its opposition to all philosophies of 'transcendence'. On that basis, it is widely believed that Deleuze's project is premised on a return to a materialist metaphysics. Christian Kerslake argues that such an interpretation is fundamentally misconceived, and has led to misunderstandings of Deleuze's philosophy, which is rather one of the latest heirs to the post-Kantian tradition of thought about immanence. This will be the first book to assess Deleuze's relationship to Kantian epistemology and post-Kantian philosophy, and will attempt to make Deleuze's philosophy intelligible to students working within that tradition. But it also attempts to reconstruct our image of the post-Kantian tradition, isolating a lineage that takes shape in the work of Schelling and Wronski, and which is developed in the twentieth century by Bergson, Warrain and Deleuze.