 At the outset of his work (TUS 1), he points out the major deficiency of our knowledge: ‘To establish cognitive criteria (pramāṇa, instruments of knowledge) depends on proper definitions. Further, to establish objects of cognitive criteria depends on cognitive criteria. When proper definitions are absent, how is it possible that one would treat both the cognitive criteria and their objects as genuinely real?’ To adopt certain definitions we first have to adopt certain definitions and criteria of validity. That has to be done vis-à-vis the external reality and tested for validity with respect to phenomena that have all the appearance of real, for Indian philosophers en bloc accepted the correspondence theory of truth. To test the definitions, criteria of validity and cognitive criteria with respect to real objects, we should first know what these real objects really are. To know that we have to have reliable instruments of knowledge (cognitive criteria) and criteria of validity at our disposal. We land in vicious circle: we can neither know cognizable real objects nor determine what genuine cognitive criteria are, nor be actually able to define them without having the idea of validity first. Without it we cannot even properly distinguish between valid cognitive procedures and invalid ones.