Nyāya realism is the idea that outward material things are complex and have structure.
Buddhists infamously reject claims like this preferring a reductionist approach in which structure is an illusion.
In this view, reality only consists of immediately accessible causal relations.
Nyāya realism consists of three claims:
1. Composite objects are robustly real.
2. Natural kinds are robustly real and reflected by general terms.
3. Cognitions have structure, because cognition reflects the structure of reality.
With our senses, we perceive things as wholes. This happens despite never sensing the entire object at once. From our senses we infer the whole of which we can later analyse the parts.
Though the whole is a composite of parts, the whole is real in Nyāya philosophy. Wholes can “do things” such as move (as a whole). In this way, the whole inheres in its parts.
The Buddhists adhere to a principle that a thing cannot both exist and not exist. This leads them to the denial of composite objects. In Nyāya things can both exist and not exist, but these things have to be delimitated correctly.
Nyāya on general terms
General terms in Nyāya can refer both to individuals and concepts. The general features manifest in all the members of the concept (similarly to Platonic forms). The general term can be perceived in the individual members. Buddhist go against this by stating that a general term must itself belong then to an even higher term. Nyāya scholars respond to this line of argument by stating that the general concept only manifests when we cognize it, thus avoiding the infinite regress. Furthermore, there must be something that helps us recognize commonality. This happens in the same way we cognize the whole by perceiving its parts
We have immediate cognitions of objects which we do not verbalize and non-immediate cognitions which are verbalized. In Nyāya both of these types of cognition are seen as structured. Nyāya philosophers hold that only structured cognitions can be true or false. Buddhists claim that structured non-immediate cognitions lead to errors because they attribute qualities to cognitions. They go on to claim that only direct perception is true. Later (in the 12th century CE) it is argued by Nyāya philosophers that the Buddhist position holds (some) truth. In order to attribute a quality to a substance, we must first cognize both eh substance and the quality in an unstructured way. Meanwhile, the Nyāya philosophers remain in their position that we can only get truth or falsehood from structured cognitions.