Full Idea
The indiscernibility of indefinitely large sizes will be a critical part of the theory of indefinitely large sizes.
Clarification
'Indiscernibility' means you can't tell the difference
Gist of Idea
The theory of infinity must rest on our inability to distinguish between very large sizes
Source
Shaughan Lavine (Understanding the Infinite [1994], VIII.2)
Book Reference
Lavine,Shaughan: 'Understanding the Infinite' [Harvard 1994], p.256