Full Idea
Cantor introduced the distinction between cardinal and ordinal numbers.
Gist of Idea
Cantor introduced the distinction between cardinals and ordinals
Source
report of George Cantor (works [1880]) by William W. Tait - Frege versus Cantor and Dedekind Intro
Book Reference
'Philosophy of Mathematics: anthology', ed/tr. Jacquette,Dale [Blackwell 2002], p.40
A Reaction
This seems remarkably late for what looks like a very significant clarification. The two concepts coincide in finite cases, but come apart in infinite cases (Tait p.58).