78 ideas
| 16227 | Philosophers are good at denying the obvious [Hawley] |
| 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] |
| 16216 | Part of the sense of a proper name is a criterion of the thing's identity [Hawley] |
| 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] |
| 16211 | A homogeneous rotating disc should be undetectable according to Humean supervenience [Hawley] |
| 16219 | Non-linguistic things cannot be indeterminate, because they don't have truth-values at all [Hawley] |
| 16223 | Maybe for the world to be vague, it must be vague in its foundations? [Hawley] |
| 16226 | Epistemic vagueness seems right in the case of persons [Hawley] |
| 16208 | Supervaluation refers to one vaguely specified thing, through satisfaction by everything in some range [Hawley] |
| 16221 | Supervaluationism takes what the truth-value would have been if indecision was resolved [Hawley] |
| 16230 | Maybe the only properties are basic ones like charge, mass and spin [Hawley] |
| 16232 | An object is 'natural' if its stages are linked by certain non-supervenient relations [Hawley] |
| 16200 | Are sortals spatially maximal - so no cat part is allowed to be a cat? [Hawley] |
| 16237 | The modal features of statue and lump are disputed; when does it stop being that statue? [Hawley] |
| 16238 | Perdurantists can adopt counterpart theory, to explain modal differences of identical part-sums [Hawley] |
| 16220 | Vagueness is either in our knowledge, in our talk, or in reality [Hawley] |
| 16222 | Indeterminacy in objects and in properties are not distinct cases [Hawley] |
| 16228 | The constitution theory is endurantism plus more than one object in a place [Hawley] |
| 16229 | Constitution theory needs sortal properties like 'being a sweater' to distinguish it from its thread [Hawley] |
| 14492 | If the constitution view says thread and sweater are two things, why do we talk of one thing? [Hawley] |
| 16193 | 'Adverbialism' explains change by saying an object has-at-some-time a given property [Hawley] |
| 16195 | Presentism solves the change problem: the green banana ceases, so can't 'relate' to the yellow one [Hawley] |
| 16202 | The problem of change arises if there must be 'identity' of a thing over time [Hawley] |
| 16192 | Endurance theory can relate properties to times, or timed instantiations to properties [Hawley] |
| 16196 | Endurance is a sophisticated theory, covering properties, instantiation and time [Hawley] |
| 16197 | How does perdurance theory explain our concern for our own future selves? [Hawley] |
| 16191 | Perdurance needs an atemporal perspective, to say that the object 'has' different temporal parts [Hawley] |
| 16199 | If an object is the sum of all of its temporal parts, its mass is staggeringly large! [Hawley] |
| 16201 | Perdurance says things are sums of stages; Stage Theory says each stage is the thing [Hawley] |
| 16240 | If a life is essentially the sum of its temporal parts, it couldn't be shorter or longer than it was? [Hawley] |
| 16203 | Stage Theory seems to miss out the link between stages of the same object [Hawley] |
| 16204 | Stage Theory says every stage is a distinct object, which gives too many objects [Hawley] |
| 16212 | An isolated stage can't be a banana (which involves suitable relations to other stages) [Hawley] |
| 16213 | Stages of one thing are related by extrinsic counterfactual and causal relations [Hawley] |
| 16206 | Stages must be as fine-grained in length as change itself, so any change is a new stage [Hawley] |
| 16205 | The stages of Stage Theory seem too thin to populate the world, or to be referred to [Hawley] |
| 16225 | If two things might be identical, there can't be something true of one and false of the other [Hawley] |
| 9723 | Sentences with 'if' are only conditionals if they can read as A-implies-B [Enderton] |
| 16239 | To decide whether something is a counterpart, we need to specify a relevant sortal concept [Hawley] |
| 16218 | On any theory of self, it is hard to explain why we should care about our future selves [Hawley] |
| 21131 | Democracy is competition for support of the people, guided by self-interest on all sides [Posner] |
| 16215 | Causation is nothing more than the counterfactuals it grounds? [Hawley] |
| 16207 | Time could be discrete (like integers) or dense (rationals) or continuous (reals) [Hawley] |