Here’s a great passage I came across in Irenaeus today that summarizes one of his main themes:
Justly, therefore, do we convict them of having departed far and wide from the truth. For if the Saviour formed the things which have been made, by means of him (the Demiurge), he is proved in that case not to be inferior but superior to them, since he is found to have been the former even of themselves; for they, too, have a place among created things. How, then, can it be argued that these men indeed are spiritual, but that he by whom they were created is of an animal nature? Or, again, if (which is indeed the only true supposition, as I have shown by numerous arguments of the very clearest nature) He (the Creator) made all things freely, and by His own power, and arranged and finished them, and His will is the substance of all things, then He is discovered to be the one only God who created all things, who alone is Omnipotent, and who is the only Father rounding and forming all things, visible and invisible, such as may be perceived by our senses and such as cannot, heavenly and earthly, “by the word of His power;” and He has fitted and arranged all things by His wisdom, while He contains all things, but He Himself can be contained by no one: He is the Former, He the Builder, He the Discoverer, He the Creator, He the Lord of all; and there is no one besides Him, or above Him, neither has He any mother, as they falsely ascribe to Him; nor is there a second God, as Marcion has imagined; nor is there a Pleroma of thirty Aeons, which has been shown a vain supposition; nor is there any such being as Bythus or Proarche; nor are there a series of heavens; nor is there a virginal light, nor an unnameable Aeon, nor, in fact, any one of those things which are madly dreamt of by these, and by all the heretics.
But there is one only God, the Creator–He who is above every Principality, and Power, and Dominion, and Virtue: He is Father, He is God, He the Founder, He the Maker, He the Creator, who made those things by Himself, that is, through His Word and His Wisdom–heaven and earth, and the seas, and all things that are in them: He is just; He is good; He it is who formed man, who planted paradise, who made the world, who gave rise to the flood, who saved Noah; He is the God of Abraham, and the God of Isaac, and the God of Jacob, the God of the living: He it is whom the law proclaims, whom the prophets preach, whom Christ reveals, whom the apostles make known s to us, and in whom the Church believes. He is the Father of our Lord Jesus Christ: through His Word, who is His Son, through Him He is revealed and manifested to all to whom He is revealed; for those [only] know Him to whom the Son has revealed Him. But the Son, eternally co-existing with the Father, from of old, yea, from the beginning, always reveals the Father to Angels, Archangels, Powers, Virtues, and all to whom He wills that God should be revealed.
Against Heresies 2.30.9 (ANF)