Chapter 18.—How Different the Uncertainty of the New Academy is from the Certainty of the Christian Faith. As regards the uncertainty about everything which Varro alleges to be the differentiating characteristic of the New Academy, the city of God thoroughly detests such doubt as madness.  Regarding matters which it apprehends by the mind and reason it has most absolute certainty, although its knowledge is limited because of the corruptible body pressing down the mind, for, as the apostle says, “We know in part.” 1290   It believes also the evidence of the senses which the mind uses by aid of the body; for [if one who trusts his senses is sometimes deceived], he is more wretchedly deceived who fancies he should never trust them.  It believes also the Holy Scriptures, old and new, which we call canonical, and which are the source of the faith by which the just lives 1291 and by which we walk without doubting whilst we are absent from the Lord. 1292   So long as this faith remains inviolate and firm, we may without blame entertain doubts regarding some things which we have neither perceived by sense nor by reason, and which have not been revealed to us by the canonical Scriptures, nor come to our knowledge through witnesses whom it is absurd to disbelieve. 1290     1 Cor. xiii. 9 . 1291     Hab. ii. 4 . 1292     2 Cor. v. 6 .