4 ideas
15927 | Definition just needs negation, known variables, conjunction, disjunction, substitution and quantification [Weyl, by Lavine] |
21548 | The null class is the class with all the non-existents as its members [MacColl, by Lackey] |
10246 | The limit of science is isomorphism of theories, with essences a matter of indifference [Weyl] |
1513 | The Egyptians were the first to say the soul is immortal and reincarnated [Herodotus] |