The initial step for us all to come to knowledge of God is contemplation of nature.
Irenaeus of Lyons[Naaman] dipped himself," it says, "seven times in Jordan." It was not for nothing that Naaman of old, when suffering from leprosy, was purified upon his being baptized, but as an indication to us. For as we are lepers in sin, we are made clean by means of the sacred water and the invocation of the Lord from our old transgressions, being spiritually regenerated as new-born babes, even as the Lord has declared: "Except a man be born again through water and the Spirit, he shall not enter into the kingdom of heaven.
Irenaeus of LyonsThe glory of God is a human being fully alive; and to be alive consists in beholding God.
Irenaeus of LyonsHe [Jesus] fought and conquered. On the one hand, he was man who struggled for his fathers and through his obedience cancelled their disobedience. On the other hand, he bound the strong one and freed the weak and bestowed salvation on his handiwork by abolishing sin. For he is our compassionate and merciful Lord who loves mankind ... Had not man conquered man's adversary, the enemy would not have been conquered justly. Again, had it not been God who bestowed salvation we would not possess it securely.
Irenaeus of LyonsSuppose there arise a dispute relative to some important question among us, should we not have recourse to the most ancient Churches with which the apostles held constant intercourse, and learn from them what is certain and clear in regard to the present question? For how should it be if the apostles themselves had not left us writings? Would it not be necessary, in that case, to follow the course of the tradition which they handed down to those to whom they did commit the Churches?
Irenaeus of Lyons