5 ideas
17832 | Zermelo showed that the ZF axioms in 1930 were non-categorical [Zermelo, by Hallett,M] |
13028 | Replacement was added when some advanced theorems seemed to need it [Zermelo, by Maddy] |
10121 | Contradiction is not a sign of falsity, nor lack of contradiction a sign of truth [Pascal] |
17626 | The antinomy of endless advance and of completion is resolved in well-ordered transfinite numbers [Zermelo] |
9626 | A structure is an abstraction, focussing on relationships, and ignoring other features [Shapiro] |