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] |
17757 | Members of ordinals are ordinals, and also subsets of ordinals [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] |
17758 | Ordinals are transitive sets of transitive sets; or transitive sets totally ordered by inclusion [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] |
12056 | An ancestral relation is either direct or transitively indirect [Wiggins] |
12050 | Substances contain a source of change or principle of activity [Wiggins] |
12052 | We never single out just 'this', but always 'this something-or-other' [Wiggins] |
12055 | Sortal predications are answers to the question 'what is x?' [Wiggins] |
12059 | A river may change constantly, but not in respect of being a river [Wiggins] |
12063 | Sortal classification becomes science, with cross reference clarifying individuals [Wiggins] |
12051 | If the kinds are divided realistically, they fall into substances [Wiggins] |
12053 | 'Human being' is a better answer to 'what is it?' than 'poet', as the latter comes in degrees [Wiggins] |
12054 | Secondary substances correctly divide primary substances by activity-principles and relations [Wiggins] |
12047 | We refer to persisting substances, in perception and in thought, and they aid understanding [Wiggins] |
12057 | Matter underlies things, composes things, and brings them to be [Wiggins] |
17742 | Scotus based modality on semantic consistency, instead of on what the future could allow [Walicki] |
7628 | Broad rejects the inferential component of the representative theory [Broad, by Maund] |
12064 | The category of substance is more important for epistemology than for ontology [Wiggins] |
12049 | Naming the secondary substance provides a mass of general information [Wiggins] |
12065 | Seeing a group of soldiers as an army is irresistible, in ontology and explanation [Wiggins] |