Books dealing with individual philosophers as well as annotated translations of their works are very much in need in the field of classical Indian philos- ophy. Hence the research efforts of modern scholars should increasingly be devoted to this objective. Professor M. Tachikawa has selected a very short elementary treatise of Udayana as well as some portions of a larger work of the same author to supplement the first. His aim is to present to us, in Udayana's own term, how he (Udayana) sees the Nyaya-VaiSe~ika system in a synoptic fashion. I wish to take this opportunity to say a few things about Udayana and the Nyaya-Vaise~ika system. UDAYANA Udayana was a pre-eminent philosopher and an astute logician of the eleventh- twelfth century India. He belonged to the Mithila region of the present Bihar 1 state. In the history of the Nyaya-V aise~a, he holds a very crucial position. In fact, two different schools of philosophy, Nyaya and Vaise~a, belonging to ancient India, merged into one in the writings of Udayana. As it has been said, in Udayana, the happy marriage between Nyaya and Vaise~ika was com- plete - the Vai e~ika ontological scheme (padiirthas or system of categories) was in this way combined with the pramiir:za doctrine (logic and a theory of knowledge) of Nyaya to produce what later came to be designated as Navya- nyaya.