"In a word, the true and the good are convertible, if what is known as true derives its being from the mind which knows it; as human science imitates divine science, wherein God, by knowing the true, begets it _internally_ in eternity, and makes it _externally_ in time. The communication of goodness to the objects of his thought is to God the criterion of the true: _vidit Deus quod essent bona_; to men it is _to have made the truth which they know_."[27] [27] Ibidem, § 1. 296. Vico's system undeniably shows him to have been a profound thinker, and to have carefully meditated the problems of intelligence. His line dividing the certainty of sciences is exceedingly interesting. At first sight, nothing is more specious than the difference marked between mathematical, natural, and moral sciences. Mathematics is absolutely certain, because the work of the understanding, it is as the understanding, which constructed them, sees them to be. On the other hand, the natural and moral sciences regard objects independent of reason, having by themselves an existence of their own; wherefore, the understanding knows little of them, and even in this little it is the more liable to err as it penetrates deeper into a sphere where it cannot construct. We call this system specious, because when examined, it is found to be destitute of all solid foundation. We recognize, however, a profound thought in its author; for one he must have had to consider science under such a point of view. 297. The understanding knows only what it makes. This proposition sums up Vico's whole system; and it must have some foundation, or he cannot advance one step without begging his question. Why does the understanding know only what it makes? Why can the problem of representation have no possible solution out of causality? We think we have shown another origin besides this in identity, also in ideality duly connected with causality. 298. To understand is not to cause. There may be, and there really is, a productive intelligence; but the act of understanding and that of causing, in general, offer distinct ideas. Intelligence supposes an activity; otherwise that intimate life which distinguishes the intelligent being is inconceivable: but this activity does not produce the objects known; it operates in an immanent manner on these objects, presupposed to be either mediately or immediately in union with the intellect.