Full Idea
For Pythagoreans, one, 1, is not a true number but the 'essence' of number, out of which the number system emerges.
Gist of Idea
For Pythagoreans 'one' is not a number, but the foundation of numbers
Source
report of Pythagoras (reports [c.530 BCE], Ch.8) by Peter Watson - Ideas Ch.8
Book Reference
Watson,Peter: 'Ideas: from fire to Freud' [Phoenix 2006], p.245
A Reaction
I think this is right! Counting and numbers only arise once the concept of individuality and identity have arisen. Counting to one is no more than observing the law of identity. 'Two' is the big adventure.