Nyāya Sūtras 201.4

201.4

tasmād rūpagrahaṇaṃ cakṣuṣaḥ, cakṣū rūpaṃ paśyati/ evaṃ ghrāṇādiṣv apīti/ tānīndriyāṇīmāni svasvaviṣayagrahaṇāc cetanāni indriyāṇāṃ bhāvābhāvayor viṣayagrahaṇasya tathābhāvāt/ evaṃ sati kim anyena cetanena?
sandhigdhatvād ahetuḥ --- yo 'yam indriyāṇāṃ bhāvābhāvayor viṣayagrahaṇasya tathābhāvaḥ, sa kiṃ cetanatvāt, āhosvic cetanopakaraṇānāṃ grahaṇanimittatvād iti sandihyate/ cetanopakaraṇatve 'pīndriyāṇāṃ grahaṇanimittatvād bhavitum arhati//2//

Therefore the apprehension of color-form belongs to the eye; the eye sees color-form. Likewise in the case of the olfactory organ and the rest. These sense organs are themselves conscious because of apprehending their respective objects, since the apprehension of the object conforms to the presence and absence of the sense organs. This being so, what is the need for another conscious entity?
[Answer:] This is a non-reason because it is doubtful: this conformity of the apprehension of an object to the presence and absence of the sense organs—is it due to their being conscious, or due to their being the cause of apprehension as instruments of a conscious entity? Thus it is doubted. Even if they are instruments of a conscious entity, it is possible because the sense organs are causes of apprehension.