Perhaps you will say, then, that creation was enough to teach men about the Father. But if that had been so, such great evils would never have occurred. Creation was there all the time, but it did not prevent men from wallowing in error. . . He deals with them as a good teacher with his pupils, coming down to their level and using simple means. St. Paul says as much: “Because in the wisdom of God the world in its wisdom knew not God. God thought fit through the simplicity of the News proclaimed to save those who believe.” Men had turned from the contemplation of God above, and were looking for Him in the opposite direction, down among the created things and things of sense. The Savior of us all, the Word of God, in His great love took to Himself a body and moved as Man among men, meeting their senses, so to speak, half way. He became Himself an object for the senses, so that those who were seeking God in sensible things might apprehend the Father through the works which He, the Word of God, did in the body. Human and human-minded as men were, therefore, to whichever side they looked in the sensible world they found themselves taught the truth. Were they awe-stricken by creation? They beheld it confessing Christ as Lord. Did their minds tend to regard men as gods? The uniqueness of the Savior’s works marked Him, alone of men, as Son of God. Were they drawn to evil spirits? They saw them driven out by the Lord and learned that the Word of God alone was God and that the evil spirits were not gods at all. Were they inclined to hero-worship and the cult of the dead? Then the fact that the Savior had risen from the dead showed them how false these other deities were, and that the Word of the Father is the one true Lord, the Lord even of death. For this reason was He both born and manifested as Man, for this He died and rose, in order that, eclipsing by His works all other human deeds, He might recall men from all the paths of error to know the Father. As He says Himself, “I came to seek and to save that which was lost.” 

On The Incarnation - Athanasius