Dignāga, (born c. 480 ce—died c. 540), was a brahmin born near Kanchipuram. He is the author of the Pramāṇa Samuccaya(Compendium of means of valid knowledge), a work that laid the foundations of Buddhist logic.
Nagarjuna, Vasubandhu, Dignaga and Dharmakirti were four great forgotten logicians from ancient India. Dignaga earlier belonged to Vatsiputriya School of Buddism which said that real personality is independent of elements (skandhas) surrounding it (akin to atman). However, Dignaga disagreed with his teacher. So he stripped himself naked and repeatedly examined himself by day and by night. This bizzare behavior was noticed and reported to Nagadatta his Upadhyaya. When Nagadatta queried abut his bizarre behaviour he was examining himself to see the real personality, different from the skandhas. Nagadatta grew angry and ordered Dignaga to leave his vihara.
Dignaga encountered Vasubandhu, who fully understood his insights, and willingly undertook to teach him Yogachara thought. Once when he was in a state of spiritual depression, Manjushri, the sword-wielding Bodhisattva of supernal wisdom, appeared to him in a vision, brought him to his senses and instructed him at great length in the Dharma. Dignaga was spiritually regenerated and retired to a cave in the Bhotashela hill in Orissa, where his intense meditation bore the inexpressible fruit of samadhi.
A few years later, a great debate was arranged at Nalanda. Dignaga was invited to debate a group of remarkable tirthikas, renowned for their dialectical agility. Dignaga defeated each one in turn so decisively that they all joined the Sangha. He wrote many volumes on Yogachara doctrine and on logic. Eventually he returned to his cave near Odissa and devoted himself to meditation. He composed the Pramanasamuccaya, aphorisms on pramana, valid knowledge. One will recall Sankara’s snake’s analogy a motif that recurs quite often in Indian arguments. However, Dignaga argues when one mistakes a rope for a snake, the error does not occur because of misperception but rather because of preconception based on fear, previous experience or memories of frightening encounters recounted by others in the past.
Such was the importance of Pramana samuccaya that Buddhists of every school, Hindus, and Jains alike felt the need to grasp its contents not only for debates, but also as an aid in understanding their own spirituality. It was translated into Chinese in the second half of the sixth century, and it remains the foundation stone of the ‘new logic’, fulfilling the prophecy of Manjushri that “in later times this Shastra will become the sole eye of all the Shastras“.