5 ideas
| 291 | Don't assume that wisdom is the automatic consequence of old age [Plato] |
| 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] |
| 15710 | Bohr explained the periodic table and chemical properties of elements, using the quantum atom [Kumar] |
| 293 | Being unafraid (perhaps through ignorance) and being brave are two different things [Plato] |