34 ideas
17749 | Post proved the consistency of propositional logic in 1921 [Walicki] |
17765 | Propositional language can only relate statements as the same or as different [Walicki] |
17764 | Boolean connectives are interpreted as functions on the set {1,0} [Walicki] |
17752 | The empty set is useful for defining sets by properties, when the members are not yet known [Walicki] |
17753 | The empty set avoids having to take special precautions in case members vanish [Walicki] |
17759 | Ordinals play the central role in set theory, providing the model of well-ordering [Walicki] |
17741 | To determine the patterns in logic, one must identify its 'building blocks' [Walicki] |
17747 | A 'model' of a theory specifies interpreting a language in a domain to make all theorems true [Walicki] |
17748 | The L-S Theorem says no theory (even of reals) says more than a natural number theory [Walicki] |
17761 | A compact axiomatisation makes it possible to understand a field as a whole [Walicki] |
17763 | Axiomatic systems are purely syntactic, and do not presuppose any interpretation [Walicki] |
20457 | Zeno assumes collecting an infinity of things makes an infinite thing [Rovelli] |
17758 | Ordinals are transitive sets of transitive sets; or transitive sets totally ordered by inclusion [Walicki] |
17755 | Ordinals are the empty set, union with the singleton, and any arbitrary union of ordinals [Walicki] |
17756 | The union of finite ordinals is the first 'limit ordinal'; 2ω is the second... [Walicki] |
17760 | Two infinite ordinals can represent a single infinite cardinal [Walicki] |
17757 | Members of ordinals are ordinals, and also subsets of ordinals [Walicki] |
17762 | In non-Euclidean geometry, all Euclidean theorems are valid that avoid the fifth postulate [Walicki] |
17754 | Inductive proof depends on the choice of the ordering [Walicki] |
20468 | Quantum mechanics deals with processes, rather than with things [Rovelli] |
20467 | Quantum mechanics describes the world entirely as events [Rovelli] |
17742 | Scotus based modality on semantic consistency, instead of on what the future could allow [Walicki] |
7903 | The six perfections are giving, morality, patience, vigour, meditation, and wisdom [Nagarjuna] |
20469 | There are probably no infinities, and 'infinite' names what we do not yet know [Rovelli] |
20461 | The basic ideas of fields and particles are merged in quantum mechanics [Rovelli] |
20462 | Because it is quantised, a field behaves like a set of packets of energy [Rovelli] |
20463 | There are about fifteen particles fields, plus a few force fields [Rovelli] |
20464 | The world consists of quantum fields, with elementary events happening in spacetime [Rovelli] |
20459 | Electrons only exist when they interact, and their being is their combination of quantum leaps [Rovelli] |
20460 | Electrons are not waves, because their collisions are at a point, and not spread out [Rovelli] |
20466 | Quantum Theory describes events and possible interactions - not how things are [Rovelli] |
20465 | Nature has three aspects: granularity, indeterminacy, and relations [Rovelli] |
20458 | The world is just particles plus fields; space is the gravitational field [Rovelli] |
20470 | Only heat distinguishes past from future [Rovelli] |