5 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] |
9390 | Logic guides thinking, but it isn't a substitute for it [Rumfitt] |
9389 | Vague membership of sets is possible if the set is defined by its concept, not its members [Rumfitt] |
13082 | The complete concept of an individual includes contingent properties, as well as necessary ones [Leibniz] |