A systematic and clear presentation of the philosophy of critical Realism as expounded by Dignaga and his school. The work is divided into two parts arranged into 26 chapters. Part I discusses the Nature of Existence, Logical Difficulties, Theory of Causation, Universals, Doctrine of Apoha, Theory of Soul and Problem of After-life. Part II deals with the Organic and Inorganic Perception, Inference and Negative Judgement. The two parts bound in one volume deal also with many subsidiary topics.