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.