Philosophical Delusion and its Therapy provides new foundations and methods for the revolutionary project of philosophical therapy pioneered by Ludwig Wittgenstein. The book vindicates this currently much-discussed project by reconstructing the genesis of important philosophical problems: With the help of concepts adapted from cognitive linguistics and cognitive psychology, the book analyses how philosophical reflection is shaped by pictures and metaphors we are not aware of employing and are prone to misapply. Through innovative case-studies on the genesis of classical problems about the mind and perception, and on thinkers including Locke, Berkeley and Ayer, the book demonstrates how such autonomous habits of thought systematically generate unsound intuitions and philosophical delusions, whose clash with reality, or among each other, gives rise to ill-motivated but maddening problems. The book re-examines models of therapeutic philosophy, due to Wittgenstein and J. L. Austin, and develops an approach that may let us overcome philosophical delusions and the problems they engender. In this way, the book explains where and why therapy in called for in philosophy, and develops techniques to carry it out.