 …for our concept to be true by the pure truth, the soul, insofar as it is informed by it, has to be similar to the truth of the thing outside, since truth is a certain adequacy of the thing and the intellect. And so, as Augustine says in bk. 2 of On Free Choice of the Will, since the soul by itself is liable to slip from truth into falsity, whence by itself it is not informed by the truth of any thing, although it can be informed by it, but nothing can inform itself, for nothing can give what it does not have; therefore, it is necessary that it be informed of the pure truth of a thing by something else. But this cannot be done by the exemplar received from the thing itself, as has been shown earlier [in the previously quoted passage — GK]. It is necessary, therefore, that it be informed by the exemplar of the unchangeable truth, as Augustine intends in the same place. And this is why he says in On True Religion that just as by its truth are true those that are true, so too by its similitude are similar those that are similar. It is necessary, therefore, that the unchangeable truth impress itself into our concept, and that it transform our concept to its own character, and that in this way it inform our mind with the expressed truth of the thing by the same similitude that the thing itself has in the first truth. [HQO a. 1, q. 2, fol. 7, I]