The paper presents characteristics of the monad and dyad which might be found
in aritmological treatise attributed to Iamblichus Chalcidensis. The treatise deals
with the nature of and relation between principles of numbers — the monad and
dyad. It contains mathematical analyses linked with traditional Greek theology, and
ontological characteristics of the principles are derived even from etymological arguments.
The treatise presents many problems, final solutions of which, for historical
reasons, needs to remain guesswork. It is probable that Iamblichus, because of his
attention for Pythagoreism, addressing the claism of Nicomachus, Antonius and “the
ancients”, was in fact presenting also fragment of his own teaching concerning numbers
and principles which organise the universe.