Apoha as Difference
The apoha theory is introduced by Dignāga as a linguistic theory of the Buddhist logico-epistemological school. Dharmakīrti, who takes over the theory from Dignāga, gives an ontological interpretation to it by calling a particular’s difference from others “exclusion” (apoha). For Dharmakīrti, it is the difference that is the foundation for conceptual construction. Conceptual cognitions and words, not connected to external entities themselves, are connected to the concepts constructed on the entities, so that they rest on the entities indirectly. Thus, the four items, namely, 1) entities, 2) differences, 3) concepts, and 4) conceptual cognitions/words are closely related.
This paper examines the function of the differences which connect concepts with entities. Conceptual cognitions/words do not numerically correspond to entities since in some cases there arises a conceptual cognition or a word concerning plural entities, or, conversely, there arise plural conceptual cognitions or words concerning an entity. These cases become explicable when the item 2) differences is put between 1) entities and 3) concepts. In explaining the relationship between conceptual cognitions and entities, Dignāga classifies the nominal entities (prajñaptisat) into three kinds: a) a spacially extended entitity (samūha); b) a temporally extended entity (saṃtāna); and c) a particular state of an entity (avasthāviśeṣa). In his Pramāṇavārttikasvavṛtti Dharmakīrti accepts this classification to explain the relationship between words and entities, putting the differences between entities and concepts, and in his Vādanyāya developes the classification into a more sophisticated form.