Nyāya Sūtras 78.9

78.9

na dravyamātraṃ na kryāmātram/ evaṃ sādhakatamādiṣv api/ evaṃ ca kārakānvākhyānaṃ yathaiva upapattita evaṃ lakṣaṇataḥ/ kārakānvākhyānam api na dravyamātre na kriyāyām vā/ kiṃ tarhi? kriyāsādhane kriyāviśeṣayukta iti/ kārakaśabdaś cāyaṃ pramāṇaṃ prameyam iti, sa ca kārakadharmaṃ na hātum arhati//16//

not a mere substance, not a mere action. So too in the case of the most effective means and the rest. And thus the grammatical explanation of grammatical roles is just as it is from reasoning, so it is from definition. The grammatical explanation of grammatical roles is also not in reference to a mere substance, nor to an action. What then? In reference to a means of action endowed with a specific action. And this word for a grammatical role is 'means of valid cognition' and 'object of valid cognition'; and it cannot abandon the nature of a grammatical role.