God knew the limitation of humanity, you see; and though the grace of being made in His Image was sufficient to give them knowledge of the Word and through Him of the Father, as a safeguard against their neglect of this grace, He provided the works of creation also as means by which the Maker might be known. Nor was this all.
Man's neglect of the indwelling grace tends ever to increase; and against this further frailty also God made provision by giving them a law, and by sending prophets, men whom they knew. Thus, if they were tardy in looking up to heaven, they might still gain knowledge of their Maker from those close at hand; for men can learn directly about higher things from other men. Three ways thus lay open to them, by which they might obtain the knowledge of God.
They could have looked up at the greatness of heaven, considered the harmony of creation, and come to know its Ruler, the Word of the Father. By His providence over all things, He makes the Father known to everyone; and for this purpose He moves all things, so that through Him everyone may know God.
Or, if this was beyond them, they could converse with holy men, and through them learn to know God, the Maker of all things, the Father of Christ, and to recognize the worship of idols as the negation of the truth and full of all impiety.
They could also have known the law, ceased from every lawless act, and lived a life of virtue. For the law was not for the Jews alone, nor were the prophets sent only for their sake. Although the prophets were sent to the Jews and were persecuted by the Jews, they were a sacred school for the whole inhabited world, teaching the knowledge of God and the conduct of the soul.
Although God’s goodness and love for humanity were so great, human beings were overcome by immediate pleasures and by the appearances and deceptions of demons. They did not lift themselves toward the truth, but filled themselves with still more evils and sins, until they no longer appeared rational but were judged irrational by their conduct.