Full Idea
One is prior to two because if there are two it follows at once that there is one, whereas if there is one there is not necessarily two.
Gist of Idea
One is prior to two, because its existence is implied by two
Source
Aristotle (Categories [c.331 BCE], 14a29)
Book Reference
Aristotle: 'Categories and De Interpretatione', ed/tr. Ackrill,J.R. [OUP 1963], p.39
A Reaction
The axiomatic introduction of a 'successor' to a number does not seem to introduce this notion of priority, based on inclusiveness. Introducing order by '>' also does not seem to indicate any logical priority.