4 ideas
9565 | Zermelo made 'set' and 'member' undefined axioms [Zermelo, by Chihara] |
3339 | For Zermelo's set theory the empty set is zero and the successor of each number is its unit set [Zermelo, by Blackburn] |
17699 | Variables are auxiliary notions, and not part of the 'eternal' essence of logic [Schönfinkel] |
468 | Musical performance can reveal a range of virtues [Damon of Ath.] |