66 ideas
| 14611 | Metaphysics should avoid talk of past, present or future [Smart] |
| 17070 | Coherence is consilience, simplicity, analogy, and fitting into a web of belief [Smart] |
| 17072 | We need comprehensiveness, as well as self-coherence [Smart] |
| 9724 | Until the 1960s the only semantics was truth-tables [Enderton] |
| 9707 | 'F(x)' is the unique value which F assumes for a value of x [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] |
| 9703 | 'dom R' indicates the 'domain' of objects having a relation [Enderton] |
| 9710 | We write F:A→B to indicate that A maps into B (the output of F on A is in B) [Enderton] |
| 13201 | ∈ says the whole set is in the other; ⊆ says the members of the subset are in the other [Enderton] |
| 13206 | A 'linear or total ordering' must be transitive and satisfy trichotomy [Enderton] |
| 13204 | The 'ordered pair' <x,y> is defined to be {{x}, {x,y}} [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] |
| 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] |
| 9701 | A 'relation' is a set of ordered pairs [Enderton] |
| 9702 | A 'domain' of a relation is the set of members of ordered pairs in the relation [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] |
| 9706 | A 'function' is a relation in which each object is related to just one other object [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] |
| 9716 | We 'partition' a set into distinct subsets, according to each relation on its objects [Enderton] |
| 9715 | An 'equivalence relation' is a reflexive, symmetric and transitive binary relation [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] |
| 9723 | Sentences with 'if' are only conditionals if they can read as A-implies-B [Enderton] |
| 17073 | I simply reject evidence, if it is totally contrary to my web of belief [Smart] |
| 7621 | Special relativity, unlike general relativity, was operationalist in spirit [Putnam on Einstein] |
| 17077 | The height of a flagpole could be fixed by its angle of shadow, but that would be very unusual [Smart] |
| 17078 | Universe expansion explains the red shift, but not vice versa [Smart] |
| 17074 | Explanations are bad by fitting badly with a web of beliefs, or fitting well into a bad web [Smart] |
| 17076 | Deducing from laws is one possible way to achieve a coherent explanation [Smart] |
| 17061 | Explanation of a fact is fitting it into a system of beliefs [Smart] |
| 17071 | An explanation is better if it also explains phenomena from a different field [Smart] |
| 17062 | If scientific explanation is causal, that rules out mathematical explanation [Smart] |
| 17075 | Scientific explanation tends to reduce things to the unfamiliar (not the familiar) [Smart] |
| 22405 | Negative utilitarianism implies that the world should be destroyed, to avoid future misery [Smart] |
| 22404 | Any group interested in ethics must surely have a sentiment of generalised benevolence [Smart] |
| 22955 | Einstein took causation to be the bedrock of physics [Einstein, by Coveney/Highfield] |
| 20638 | General relativity assumes laws of nature are the same in all frames of reference [Einstein, by Close] |
| 20636 | Newton is a special case of Einstein's general theory, with an infinite speed of light [Einstein, by Close] |
| 21230 | The theory is 'special' because it sticks to observers moving straight, at constant speeds [Einstein, by Farmelo] |
| 21231 | Assume the speed of light is constant for all observers, and the laws of physics are the same [Einstein, by Farmelo] |
| 14613 | Special relativity won't determine a preferred frame, but we can pick one externally [Smart] |
| 20634 | General Relativity says there is no absolute force or acceleration [Einstein, by Close] |
| 17063 | Unlike Newton, Einstein's general theory explains the perihelion of Mercury [Smart] |
| 20648 | Mass is a measure of energy content [Einstein] |
| 21232 | Space-time arises from the connection between measurements of space and of time [Einstein, by Farmelo] |
| 14615 | If time flows, then 'how fast does it flow?' is a tricky question [Smart] |
| 14614 | The past, present, future and tenses of A-theory are too weird, and should be analysed indexically [Smart] |
| 7626 | I do not believe in a personal God [Einstein] |