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] |
6019 | If someone squashed a horse to make a dog, something new would now exist [Mnesarchus] |
5880 | Xenocrates held that the soul had no form or substance, but was number [Xenocrates, by Cicero] |