This book may be the first in English to present the Nyingma-lineage understanding of valid cognition in Buddhism and in the Vajrayana in particular. The translation is a clear and concise primer on higher realization through valid cognition in Buddhist philosophy. It poses and answers the questions: How can we know the two truths--the relative truth of conventional appearances and the absolute truth of emptiness and buddha nature--and how can we be certain our knowledge is accurate? It includes the sutra presentation of the two truths and the tantra teachings of the two truths as the purity and equality of all phenomena. It will give Westerners a solid foundation in valid cognition through direct perception and reasoning according to the traditional Indian treatises of Dharmakirti and Dignaga.