 As with Dharmakīrti, Śāntarakṣita describes valid knowledge or valid cognitions as instants of new knowledge in the sense that the cognizer knows newly something which to that point was unknown. Generally speaking, Buddhist pramāṇavāda thinkers categorize two types of  pramāṇa[16]:  perception  (pratyakṣa)[17]  and inference (anumāna). Objects of perception are causally efficacious particulars (svalakṣaṇa), actual instance of things in the world with temporal and spatial location. It is only particulars that are considered to be real. Generally, it would be thought that words apply to universals (sāmānyalakṣaṇa) which are conceptual constructs that have no causal efficacy in the world. Thus the early pramāṇavāda thinkers like Dignāga and Dharmakīrti can be considered to hold a soft form of connotationism in that they would reject a denotationist view that considers words to apply directly to actual particulars. The intuition that a word points to a particular would be very objectionable. A word cannot express a particular because particulars are limitless and words have limits. Yet they are soft connotationists in that via a process of elimination or exclusion, they posit a way in which language is both not arbitrary and not a reference to particulars. Inferences are cognitions based on valid reasons that depend on this non-arbitrary use of  language.[18]