6 Again, as to the desire they exhibit to refer this whole universe to numbers, they have learned it from the Pythagoreans. For these were the first who set forth numbers as the initial principle of all things, and [described] that initial principle of theirs as being both equal and unequal, out of which [two properties] they conceived that both things sensible and immaterial derived their origin. And [they held] that one set of first principles gave rise to the matter [of things], and another to their form.
They affirm that from these first principles all things have been made, just as a statue is of its metal and its special form. Now, the heretics have adapted this to the things which are outside of the Pleroma. The [Pythagoreans] maintained that the principle of intellect is proportionate to the energy wherewith mind, as a recipient of the comprehensible, pursues its inquiries, until, worn out, it is resolved at length in the Indivisible and One. They further affirm that Hen— that is, One— is the first principle of all things, and the substance of all that has been formed.
From this again proceeded the Dyad, the Tetrad, the Pentad, and the manifold generation of the others. These things the heretics repeat, word for word, with a reference to their Pleroma and Bythus. From the same source, too, they strive to bring into vogue those conjunctions which proceed from unity. Marcus boasts of such views as if they were his own, and as if he were seen to have discovered something more novel than others, while he simply sets forth the Tetrad of Pythagoras as the originating principle and mother of all things.
Source: Adversus haereses (New Advent)