Full Idea
Number is nothing but the actual numbered things themselves. Hence just as unity is not an accident added to the thing which is one, so number is not an accident of the things which are numbered.
Clarification
An 'accident' is the Aristotelian word for a property
Gist of Idea
Just as unity is not a property of a single thing, so numbers are not properties of many things
Source
William of Ockham (Summa totius logicae [1323], I.c.xliv)
Book Reference
Ockham,William of: 'Ockham's Philosophical Writings', ed/tr. Boehner,P [Hackett 1990], p.138
A Reaction
[William does not necessarily agree with this view] It strikes me as a key point here that any account of the numbers had better work for 'one', though 'zero' might be treated differently. Some people seem to think unity is a property of things.