11 ideas
| 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] |
| 9295 | Not only substances have attributes; events, actions, states and qualities can have them [Teichmann] |
| 6019 | If someone squashed a horse to make a dog, something new would now exist [Mnesarchus] |
| 9293 | Body-spirit interaction ought to result in losses and increases of energy in the material world [Teichmann] |
| 9294 | No individuating marks distinguish between Souls [Teichmann] |
| 9292 | The Soul has no particular capacity (in the way thinking belongs to the mind) [Teichmann] |