28 ideas
18901 | Truthmakers are facts 'of' a domain, not something 'in' the domain [Sommers] |
18904 | 'Predicable' terms come in charged pairs, with one the negation of the other [Sommers, by Engelbretsen] |
18895 | Logic which maps ordinary reasoning must be transparent, and free of variables [Sommers] |
10888 | Sets can be defined by 'enumeration', or by 'abstraction' (based on a property) [Zalabardo] |
10889 | The 'Cartesian Product' of two sets relates them by pairing every element with every element [Zalabardo] |
10890 | A 'partial ordering' is reflexive, antisymmetric and transitive [Zalabardo] |
10886 | Determinacy: an object is either in a set, or it isn't [Zalabardo] |
10887 | Specification: Determinate totals of objects always make a set [Zalabardo] |
10897 | A first-order 'sentence' is a formula with no free variables [Zalabardo] |
10893 | Γ |= φ for sentences if φ is true when all of Γ is true [Zalabardo] |
10899 | Γ |= φ if φ is true when all of Γ is true, for all structures and interpretations [Zalabardo] |
18897 | Predicate logic has to spell out that its identity relation '=' is an equivalent relation [Sommers] |
18893 | Translating into quantificational idiom offers no clues as to how ordinary thinkers reason [Sommers] |
10896 | Propositional logic just needs ¬, and one of ∧, ∨ and → [Zalabardo] |
18903 | Sommers promotes the old idea that negation basically refers to terms [Sommers, by Engelbretsen] |
18894 | Predicates form a hierarchy, from the most general, down to names at the bottom [Sommers] |
10898 | The semantics shows how truth values depend on instantiations of properties and relations [Zalabardo] |
10902 | We can do semantics by looking at given propositions, or by building new ones [Zalabardo] |
10892 | We make a truth assignment to T and F, which may be true and false, but merely differ from one another [Zalabardo] |
10900 | Logically true sentences are true in all structures [Zalabardo] |
10895 | 'Logically true' (|= φ) is true for every truth-assignment [Zalabardo] |
10901 | Some formulas are 'satisfiable' if there is a structure and interpretation that makes them true [Zalabardo] |
10894 | A sentence-set is 'satisfiable' if at least one truth-assignment makes them all true [Zalabardo] |
10903 | A structure models a sentence if it is true in the model, and a set of sentences if they are all true in the model [Zalabardo] |
10891 | If a set is defined by induction, then proof by induction can be applied to it [Zalabardo] |
18900 | Unfortunately for realists, modern logic cannot say that some fact exists [Sommers] |
18284 | Particulars can be verified or falsified, but general statements can only be falsified (conclusively) [Popper] |
18898 | In standard logic, names are the only way to refer [Sommers] |