syād etat yadi vedasyāpauruṣeyatvam evaṃ prasādhya prāmāṇyaṃ prasādhyate, hanta tarhi parataḥ prāmāṇyaṃ prayuktaṃ vedasya
This might be [objected]: if the authorlessness of the Veda is thus proved and [then] its validity is proved, then, alas, the validity of the Veda would depend on something external.