30 ideas
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] |
10653 | Maybe set theory need not be well-founded [Varzi] |
10887 | Specification: Determinate totals of objects always make a set [Zalabardo] |
10648 | Mereology need not be nominalist, though it is often taken to be so [Varzi] |
10655 | Are there mereological atoms, and are all objects made of them? [Varzi] |
10659 | There is something of which everything is part, but no null-thing which is part of everything [Varzi] |
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] |
10896 | Propositional logic just needs ¬, and one of ∧, ∨ and → [Zalabardo] |
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] |
10895 | 'Logically true' (|= φ) is true for every truth-assignment [Zalabardo] |
10900 | Logically true sentences are true in all structures [Zalabardo] |
10894 | A sentence-set is 'satisfiable' if at least one truth-assignment makes them all true [Zalabardo] |
10901 | Some formulas are 'satisfiable' if there is a structure and interpretation that makes them 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] |
10661 | 'Composition is identity' says multitudes are the reality, loosely composing single things [Varzi] |
10647 | Parts may or may not be attached, demarcated, arbitrary, material, extended, spatial or temporal [Varzi] |
10649 | 'Part' stands for a reflexive, antisymmetric and transitive relation [Varzi] |
10651 | If 'part' is reflexive, then identity is a limit case of parthood [Varzi] |
10654 | The parthood relation will help to define at least seven basic predicates [Varzi] |
10658 | Sameness of parts won't guarantee identity if their arrangement matters [Varzi] |
10652 | Conceivability may indicate possibility, but literary fantasy does not [Varzi] |
20653 | Six reduction levels: groups, lives, cells, molecules, atoms, particles [Putnam/Oppenheim, by Watson] |