63 ideas
| 9724 | Until the 1960s the only semantics was truth-tables [Enderton] |
| 9703 | 'dom R' indicates the 'domain' of objects having a relation [Enderton] |
| 9705 | 'fld R' indicates the 'field' of all objects in the relation [Enderton] |
| 9704 | 'ran R' indicates the 'range' of objects being related to [Enderton] |
| 9710 | We write F:A→B to indicate that A maps into B (the output of F on A is in B) [Enderton] |
| 9707 | 'F(x)' is the unique value which F assumes for a value of x [Enderton] |
| 13201 | ∈ says the whole set is in the other; ⊆ says the members of the subset are in the other [Enderton] |
| 9712 | A relation is 'symmetric' on a set if every ordered pair has the relation in both directions [Enderton] |
| 9713 | A relation is 'transitive' if it can be carried over from two ordered pairs to a third [Enderton] |
| 13204 | The 'ordered pair' <x,y> is defined to be {{x}, {x,y}} [Enderton] |
| 13206 | A 'linear or total ordering' must be transitive and satisfy trichotomy [Enderton] |
| 9699 | The 'powerset' of a set is all the subsets of a given set [Enderton] |
| 9700 | Two sets are 'disjoint' iff their intersection is empty [Enderton] |
| 9702 | A 'domain' of a relation is the set of members of ordered pairs in the relation [Enderton] |
| 9701 | A 'relation' is a set of ordered pairs [Enderton] |
| 9706 | A 'function' is a relation in which each object is related to just one other object [Enderton] |
| 9708 | A function 'maps A into B' if the relating things are set A, and the things related to are all in B [Enderton] |
| 9709 | A function 'maps A onto B' if the relating things are set A, and the things related to are set B [Enderton] |
| 9711 | A relation is 'reflexive' on a set if every member bears the relation to itself [Enderton] |
| 9714 | A relation satisfies 'trichotomy' if all pairs are either relations, or contain identical objects [Enderton] |
| 9717 | A set is 'dominated' by another if a one-to-one function maps the first set into a subset of the second [Enderton] |
| 13200 | Note that {Φ} =/= Φ, because Φ ∈ {Φ} but Φ ∉ Φ [Enderton] |
| 13199 | The empty set may look pointless, but many sets can be constructed from it [Enderton] |
| 13203 | The singleton is defined using the pairing axiom (as {x,x}) [Enderton] |
| 9715 | An 'equivalence relation' is a reflexive, symmetric and transitive binary relation [Enderton] |
| 9716 | We 'partition' a set into distinct subsets, according to each relation on its objects [Enderton] |
| 13202 | Fraenkel added Replacement, to give a theory of ordinal numbers [Enderton] |
| 13205 | We can only define functions if Choice tells us which items are involved [Enderton] |
| 9722 | Inference not from content, but from the fact that it was said, is 'conversational implicature' [Enderton] |
| 9718 | Validity is either semantic (what preserves truth), or proof-theoretic (following procedures) [Enderton] |
| 9721 | A logical truth or tautology is a logical consequence of the empty set [Enderton] |
| 9994 | A truth assignment to the components of a wff 'satisfy' it if the wff is then True [Enderton] |
| 9719 | A proof theory is 'sound' if its valid inferences entail semantic validity [Enderton] |
| 9720 | A proof theory is 'complete' if semantically valid inferences entail proof-theoretic validity [Enderton] |
| 9995 | Proof in finite subsets is sufficient for proof in an infinite set [Enderton] |
| 9996 | Expressions are 'decidable' if inclusion in them (or not) can be proved [Enderton] |
| 9997 | For a reasonable language, the set of valid wff's can always be enumerated [Enderton] |
| 12887 | A whole must have one characteristic, an internal relation, and a structure [Rescher/Oppenheim] |
| 9723 | Sentences with 'if' are only conditionals if they can read as A-implies-B [Enderton] |
| 17979 | Research shows perceptual discrimination is sharper at category boundaries [Murphy] |
| 18690 | Induction is said to just compare properties of categories, but the type of property also matters [Murphy] |
| 17980 | The main theories of concepts are exemplar, prototype and knowledge [Murphy] |
| 17973 | The theoretical and practical definitions for the classical view are very hard to find [Murphy] |
| 17969 | The classical definitional approach cannot distinguish typical and atypical category members [Murphy] |
| 17970 | Classical concepts follow classical logic, but concepts in real life don't work that way [Murphy] |
| 17971 | Classical concepts are transitive hierarchies, but actual categories may be intransitive [Murphy] |
| 17972 | The classical core is meant to be the real concept, but actually seems unimportant [Murphy] |
| 17975 | There is no 'ideal' bird or dog, and prototypes give no information about variability [Murphy] |
| 17976 | Prototypes are unified representations of the entire category (rather than of members) [Murphy] |
| 18691 | The prototype theory uses observed features, but can't include their construction [Murphy] |
| 17983 | The prototype theory handles hierarchical categories and combinations of concepts well [Murphy] |
| 17985 | Prototypes theory of concepts is best, as a full description with weighted typical features [Murphy] |
| 17986 | Learning concepts is forming prototypes with a knowledge structure [Murphy] |
| 17974 | The most popular theories of concepts are based on prototypes or exemplars [Murphy] |
| 17977 | The exemplar view of concepts says 'dogs' is the set of dogs I remember [Murphy] |
| 17982 | Exemplar theory struggles with hierarchical classification and with induction [Murphy] |
| 17981 | Children using knowing and essentialist categories doesn't fit the exemplar view [Murphy] |
| 17984 | Conceptual combination must be compositional, and can't be built up from exemplars [Murphy] |
| 17987 | The concept of birds from exemplars must also be used in inductions about birds [Murphy] |
| 17978 | We do not learn concepts in isolation, but as an integrated part of broader knowledge [Murphy] |
| 18687 | Concepts with familiar contents are easier to learn [Murphy] |
| 18688 | Some knowledge is involved in instant use of categories, other knowledge in explanations [Murphy] |
| 18689 | People categorise things consistent with their knowledge, even rejecting some good evidence [Murphy] |