Full Idea
Geometers talk as if they were actually doing something, and the point of their theorems is to have some effect (like 'squaring'). ...But the sole purpose is knowledge, of things which exist forever, not coming into existence and passing away.
Gist of Idea
Geometry is not an activity, but the study of unchanging knowledge
Source
Plato (The Republic [c.371 BCE], 527a)
Book Reference
Plato: 'Republic', ed/tr. Waterfield,Robin [OUP 1993], p.258
A Reaction
Modern Constructivism defends the view which Plato is attacking. The existence of real infinities can be doubted simply because we have not got enough time to construct them.