Insanity - in clinical practice as in the popular imagination - is seen as a state of believing things that are not true and perceiving things that do not exist. Most schizophrenics, however, do not act as if they mistake their delusions for reality. In a work of uncommon insight and empathy, Louis A. Sass shatters conventional thinking about insanity by juxtaposing the narratives of delusional schizophrenics with the philosophical writings of Ludwig Wittgenstein. In the formative years of psychiatry Freud, Bleuler, and Jaspers all studied Daniel Paul Schreber's Memoirs of My Nervous Illness as a model of psychotic thought. Sass provides a nuanced interpretation of Schreber's Memoirs in the context of Wittgenstein's analysis of philosophical solipsism. A dauntless critic of the illusions of philosophy, Wittgenstein likened the speculative excesses of traditional metaphysics to mental illness. Sass observes that many of the "intellectual diseases" that Wittgenstein discerned - diseases involving detachment from social existence and practical concerns, and exaggerated processes of abstraction and self-consciousness - have striking affinities with the symptoms of schizophrenia. Like the philosophical solipsist, the schizophrenic may define his or her own consciousness as the center of the universe - and may experience his or her delusional world as a product of that same consciousness. Schizophrenia, Sass demonstrates, is not the loss of rationality, but the far point in the trajectory of a consciousness turned in upon itself. The Paradoxes of Delusion will be necessary reading for anyone concerned with the preoccupations of modern philosophy and the realities of mental illness.