III. To the Principal Arguments
121. To the principal reasons. To the first reason [n.95]. To the minor I reply that the law of nature was content with fewer things, which were passed down by memory from fathers to sons. Those men were also more endowed in natural powers, and therefore a modicum of inspired doctrine was able to suffice them. Or it should otherwise be said to this instance, and to the one about the law of Moses, that the ordered progress of Scripture showed the fittingness of it. The thing is made plain by Augustine 83 Questions q.53 n.4.
122. To the second reason [n.96] I say that one grasps more delightfully a thing that lies hid under some literal statement than if it were said expressly; and for this reason the fact that what is express in the New Testament was veiled under figures in the Old contributes to devotion; and this as to the ceremonies; but as to the histories, both these and the ceremonies are examples declarative of the law. Likewise, from the whole progress of Scripture is made plain an ordered government with respect to man and the whole creation.
123. To the third reason [n.97], Origen in his homily On Noah’s Ark [Homilies on Genesis, hom. 2 n.1]: “In Scripture silence seems to have been considered appropriate on this point, which would be sufficiently taught by the nature of the consequence itself.”41 Hence many necessary truths are not express in Sacred Scripture, although they are virtually contained there as conclusions in the principles; the labor of doctors and expositors has been useful for the investigation of these things.
If you object that about many things in human acts it is doubtful whether they are mortal sins or not, even after one supposes all the teachings of the doctors and expositors, - I reply: the way of salvation is not in doubt, because a man ought to guard himself from such doubtful things as from things dangerous, lest, while he is exposing himself to the danger, he fall into sin. But if someone wants to seek salvation yet carelessly 42exposes himself to the danger, although there would perhaps, by the nature of the act, be no mortal sin, nevertheless he will sin mortally by exposing himself to such danger, as will be touched on elsewhere [4 d.5 q.3 n.2; d.30 q.1 nn.4-5].