The System of the Vedanta according to Badarayana's Brahma-Sutras and Cankara's Commentary c6.s2.t6.2

c6.s2.t6.2

“For it is that which brings into use all means of proof, such as perception and the like, in order to prove a thing which is not known. For the objects of the expressions ether etc. require a proof, because they are not assumed as known of themselves. But the Self is the basis (âçraya) of the action of proving, and consequently it is evident before the action of proving. And since it is of this character, it is therefore impossible to deny it. For we can call in question something, which comes to us (âgantuka) [from outside], but not that which is our own being. For it is even the own being of him who calls it in question [cf. p. 79, l. 823, 2]; fire cannot call its own heat in question. And further, when it is said: ‘It is I, who now know what at present exists, it is I, who knew the past, and what was before the past, it is I, who shall know the future and what is after the future,’ it is implied in these words that even when the object of knowledge alters, the knower does not alter, because he is in the past, future, and present; for his essence is eternally present (sar-vadâ-vartamâna-svabhâvatvâd); therefore, even when the body turns to ashes, there is no passing away of the Self, for its essence is the present, yea, it is not even for a moment thinkable, that its essence should be anything else than this.”