9 ideas
21336 | Crates lived in poverty, and treated his whole life as a joke [Crates of Thebes, by Plutarch] |
1767 | Everyone should study philosophy until they see all people in the same light [Crates of Thebes, by Diog. Laertius] |
11022 | Gentzen introduced a natural deduction calculus (NK) in 1934 [Gentzen, by Read] |
11065 | The inferential role of a logical constant constitutes its meaning [Gentzen, by Hanna] |
11023 | The logical connectives are 'defined' by their introduction rules [Gentzen] |
11213 | Each logical symbol has an 'introduction' rule to define it, and hence an 'elimination' rule [Gentzen] |
13832 | Natural deduction shows the heart of reasoning (and sequent calculus is just a tool) [Gentzen, by Hacking] |
10067 | Gentzen proved the consistency of arithmetic from assumptions beyond arithmetic [Gentzen, by Musgrave] |
1513 | The Egyptians were the first to say the soul is immortal and reincarnated [Herodotus] |