Full Idea
I can start with a triangle, and rise by degrees to all straight-lined figures and to extension itself. The lower degree will include the higher degree. Since the higher degree is less determinate, it can represent more things.
Gist of Idea
We can rise by degrees through abstraction, with higher levels representing more things
Source
Arnauld / Nicole (Logic (Port-Royal Art of Thinking) [1662], I.5)
Book Reference
Arnauld,A/Nicole,P: 'Logic, or the Art of Thinking (Port-Royal)', ed/tr. Buroker,J.V. [CUP 1996], p.38
A Reaction
[compressed] This attempts to explain the generalising ability of abstraction cited in Idea 10501. If you take a complex object and eliminate features one by one, it can only 'represent' more particulars; it could hardly represent fewer.
Related Idea
Idea 10501 A triangle diagram is about all triangles, if some features are ignored [Arnauld,A/Nicole,P]