This book explores the potential relevance of the Upanishads, a corpus of ancient Eastern apophatic texts, to contemporary Western theories of consciousness and psychopathology, particularly in relation to psychoanalysis, neuroscience, and schizophrenia-spectrum disorders. Beginning with an analysis of Upanishadic thought and its historical influence in Europe, this work bridges the gap between ancient wisdom and modern scientific inquiry. It examines the dream theories of psychoanalyst Wilfred Bion in relation to Upanishadic conceptions of the Self, followed by an exploration of contemporary neuroscientific perspectives on selfhood. Further, it delves into the evolution and function of sleep and dreaming in Homo sapiens, proposing a novel heuristic: that schizophrenia-spectrum disorders may be developmentally linked to alterations in the sleep and dreaming systems of the human mind-brain. Offering a unique interdisciplinary synthesis, this text will appeal to scholars and students of philosophy, psychology, neuroscience, and religious studies, as well as those interested in the intersections of ancient meditative traditions and modern scientific paradigms.