Full Idea
There is nothing contrary to substances,…. and a substance does not admit of a more and a less. If this substance is a man, it will not be more a man or less a man either than itself or than another man.
Gist of Idea
Substances have no opposites, and don't come in degrees (including if the substance is a man)
Source
Aristotle (Categories [c.331 BCE], 03b33)
Book Reference
Aristotle: 'Categories and De Interpretatione', ed/tr. Ackrill,J.R. [OUP 1963], p.10