As we have said earlier, Patanjali has singled out pramana, or “valid”, “true” knowledge, as the first vritti. However it strikes the eye here that, unlike with all other vrittis, when speaking about pramana the Yoga Sutras author has not only provided its definition but has also listed the main concepts of traditional Indian gnoseology. That is, he has listed the "right" sources of knowledge: the direct (own) perception, the authoritative evidence and the logical inference. In general such view is inherent in many theories of gnoseology of Indian philosophical systems (see, for instance, the "Indian Philosophy"of S. Radhakrishnan). Moreover, in some systems they used to single out not three sources of knowledge, as Patanjali did, but four of them, adding the mystical knowledge as an additional "valid" means. Thus there come two questions:
1. Why was Patanjali that specific in distinguishing pramana if it is just the same vritti?
2. Why did Patanjali, being a mystic, ignore singling out mystical knowledge as a “valid” means of obtaining the true knowledge?
