19 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] |
| 18085 | Values that approach zero, becoming less than any quantity, are 'infinitesimals' [Cauchy] |
| 18084 | When successive variable values approach a fixed value, that is its 'limit' [Cauchy] |
| 10067 | Gentzen proved the consistency of arithmetic from assumptions beyond arithmetic [Gentzen, by Musgrave] |
| 20429 | Most of us are too close to our own motives to understand them [Fry] |
| 20424 | Imaginative life requires no action, so new kinds of perception and values emerge in art [Fry] |
| 20427 | Everyone reveals an aesthetic attitude, looking at something which only exists to be seen [Fry] |
| 20433 | 'Beauty' can either mean sensuous charm, or the aesthetic approval of art (which may be ugly) [Fry] |
| 20430 | In life we neglect 'cosmic emotion', but it matters, and art brings it to the fore [Fry] |
| 20431 | Art needs a mixture of order and variety in its sensations [Fry] |
| 20423 | If graphic arts only aim at imitation, their works are only trivial ingenious toys [Fry] |
| 20428 | Popular opinion favours realism, yet most people never look closely at anything! [Fry] |
| 20432 | When viewing art, rather than flowers, we are aware of purpose, and sympathy with its creator [Fry] |
| 20425 | In the cinema the emotions are weaker, but much clearer than in ordinary life [Fry] |
| 20426 | For pure moralists art must promote right action, and not just be harmless [Fry] |