The Indefinite Dyad

Alongside the One, the tradition speaks of an Indefinite Dyad — the 'great and small', the principle of multiplicity, unlimitedness, and difference. Where the One imposes limit, unity, and form, the Dyad supplies the boundless, indeterminate material on which limit is imposed. From the interaction of the two arise number, the Forms, and ultimately all things — the One as the principle of determination, the Dyad as the principle of plurality.

The unwritten teachings

This pairing belongs to the so-called unwritten teachings of Plato — doctrines he is said to have expounded orally in the Academy rather than in the dialogues. They are reported, often critically, by Aristotle, and were developed by Plato's successors Speusippus and Xenocrates. The scheme carries a strong Pythagorean stamp, deriving the cosmos from the fundamental opposition of limit and the unlimited.

In Neoplatonism

The theme reappears in Neoplatonism as the moment of indefiniteness in the procession from the One: the indeterminate power that first flows out must be informed and turned back toward its source before it becomes determinate being, as Intellect takes shape. The Dyad is thus woven into the very generation of reality.