Sarvadarshanasangraha 2.87

2.87

anye tu manyante/ yathoktaṃ bāhyaṃ vastujātaṃ nāstīti tad ayuktam/ pramāṇābhāvāt/ na ca sahopalambhaniyamaḥ pramāṇam iti vaktavyam/ vedyavedakayor abhedasādhakatvenābhimatasya tasyāprayojakatvena saṃdigdhavipakṣavyāvṛttikatvāt/

Others again (the Sautrāntikas) hold that the position that there is no external world is untenable, as wanting evidence. Nor (they contend) can it be maintained that invariability of simultaneous cognition is an evidence, for this simultaneous cognition which you accept as proof of the identity of subject and object is indecisive, being found in dubious and in contrary instances. If you rejoin (they proceed): Let there be a proof of this identity, and let this proof be invariability of simultaneous cognition,—we refuse this, because inasmuch as cognition must ultimately have some object, it is manifested in duality, and because such invariability of simultaneity as to time and place is impossible. Moreover (they continue), if the object, blue or whatever it be, were only a form of cognition, it should be presented as Ego, not as Hoc aliquid, because the cognition and the object would be identical. Perhaps you will say: A blue form consisting of cognition is illusorily presented as external and as other than self, and consequently the Ego is not suggested; and so it has been said—