Full Idea
If a man had a positive idea of infinite, either duration or space, he could add two infinities together; nay, make one Infinite infinity bigger than another, absurdities too gross to be confuted.
Gist of Idea
If there were real infinities, you could add two together, which is ridiculous
Source
John Locke (Essay Conc Human Understanding (2nd Ed) [1694], 2.17.20)
Book Reference
Locke,John: 'Essay Concerning Human Understanding', ed/tr. Nidditch,P.H. [OUP 1979], p.222
A Reaction
A beautifully heartfelt objection to everything Cantor stood for, two hundred years before Cantor got round to it.