Full Idea
What is really essential to being a natural number is what is common to the natural numbers in all the functions they perform.
Gist of Idea
The essence of natural numbers must reflect all the functions they perform
Source
Jeffrey H. Sicha (Counting and the Natural Numbers [1968], 2)
Book Reference
-: 'Philosophy of Science' [-], p.407
A Reaction
I could try using natural numbers as insults. 'You despicable seven!' 'How dare you!' I actually agree. The question about functions is always 'what is it about this thing that enables it to perform this function'.