 More substantial debates on the nature of perception focus on the adjectives in the latter part of the sūtra, viz., non-verbal (avyapadeśyam), non-erroneous or non-deviating (avyabhichāri), and well-ascertained or free from doubt (vyavasāyātmaka). There is some disagreement among the Naiyāyika commentators about the interpretations of the adjectives non-verbal and well-ascertained. Vātsyāyana, in his commentary on the Nyāya-sūtra, argues that the adjectives non-verbal and well-ascertained are really part of the definition; non-verbal to point out that perceptual knowledge is not associated with words (Bhartṛhari, the famous Grammarian, on the other hand, holds that awareness is necessarily constituted by words and apprehended through them) and well-ascertained to affirm that perceptual knowledge is only of a definite particular and specifically excludes situations in which the perceiver may be in doubt whether a perceived object ‘a’ is an F or a G. Vācaspati Miśra, argues that the adjective well-ascertained need not be used to exclude the so-called perception in the form of doubt, as doubtful knowledge, being invalid, is already excluded by the adjective non-erroneous. Rather, the term vyavasāyātmaka stands for determinate perceptual judgment. Thus understood, the adjectives non-verbal and determinate seem to be complementary; a piece of non-verbal perceptual knowledge cannot be said to be, at the same time, determinate. Vācaspati Miśra posits that these two adjectives indicate two different forms of perceptual cognition and are not to be regarded as its defining characteristics. According to him, Gautama included these adjectives to identify two kinds of perceptual knowledge: avyapadeśyam indicates non-conceptual or non-verbal perception and vyavasāyātmaka indicates conceptual or determinate perceptions. He contends that by the term non-verbal, Gautama refutes the Grammarian view and includes non-conceptual perception and, by the term well-ascertained, he refutes the Buddhist view and includes conceptual or judgemental perceptions as valid. Pradyot Mondal (1982) traces the history of this controversy among Naiyāyikas. He offers overwhelming scholarly evidence in favor of the view that Naiyāyikas mostly regard the adjectives as part of the definition of perception and do not agree with Vācaspati’s interpretation. For most Naiyāyikas “non-verbal” is included to deny the causal role of words in origination of perceptual cognition and, therefore, it applies to non-conceptual and conceptual perceptions both, the difference being that the former is inexpressible in language, while the latter is not. Thus Mondal claims that the adjective “non-verbal” is sufficient on its own to reject the Grammarian and the Buddhist views of perception. The Nyāya pphilosophers seek the middle ground between these positions to defend their thoroughly realist view. They argue that their is some mental shaping in almost all perceptual events, memory dispositions acquired on account of previous experiences are among the causal factors contributing to the current perception. Perceptual experience in this sense is laden with or infused by concepts. This, however, does not compromise the realism, since the concepts themselves are repeatable features of real objects and are perceptually acquired in past encounters with these features. For perception to be a source of knowledge it must be concept-laden, such that it is verbalizable and determinate (Phillips, 2019). The exact role of concepts in perception—in dispute in the Nyāya/Buddhist debate—will be discussed in the next section.