Nor let the use of the future tense perplex you: that hearing is eternal, because the knowledge is eternal. To that which is eternal, without beginning, and without end, a verb of any tense may be applied. For though an unchangeable nature does not admit of was, and shall be, but only is, yet it is allowable to say of It, was, and is, and shall be; was, because It never began; shall be, because It never shall end; is, because It always is.
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).
Also cites: Tr. xcix