138 ideas
9593 | Progress in philosophy is incremental, not an immature seeking after drama [Williamson] |
9184 | We can't presume that all interesting concepts can be analysed [Williamson] |
6859 | Analytic philosophy has much higher standards of thinking than continental philosophy [Williamson] |
9955 | Contextual definitions replace a complete sentence containing the expression [George/Velleman] |
10031 | Impredicative definitions quantify over the thing being defined [George/Velleman] |
21616 | Truth and falsity apply to suppositions as well as to assertions [Williamson] |
21623 | True and false are not symmetrical; false is more complex, involving negation [Williamson] |
15134 | The truthmaker principle requires some specific named thing to make the difference [Williamson] |
15141 | Truthmaker is incompatible with modal semantics of varying domains [Williamson] |
15140 | The converse Barcan formula will not allow contingent truths to have truthmakers [Williamson] |
9594 | Correspondence to the facts is a bad account of analytic truth [Williamson] |
14626 | In S5 matters of possibility and necessity are non-contingent [Williamson] |
15131 | If metaphysical possibility is not a contingent matter, then S5 seems to suit it best [Williamson] |
15135 | If the domain of propositional quantification is constant, the Barcan formulas hold [Williamson] |
15130 | If a property is possible, there is something which can have it [Williamson] |
15139 | Converse Barcan: could something fail to meet a condition, if everything meets that condition? [Williamson] |
21602 | Many-valued logics don't solve vagueness; its presence at the meta-level is ignored [Williamson] |
6862 | Fuzzy logic uses a continuum of truth, but it implies contradictions [Williamson] |
10098 | The 'power set' of A is all the subsets of A [George/Velleman] |
10099 | The 'ordered pair' <a, b>, for two sets a and b, is the set {{a, b},{a}} [George/Velleman] |
10101 | Cartesian Product A x B: the set of all ordered pairs in which a∈A and b∈B [George/Velleman] |
10103 | Grouping by property is common in mathematics, usually using equivalence [George/Velleman] |
10104 | 'Equivalence' is a reflexive, symmetric and transitive relation; 'same first letter' partitions English words [George/Velleman] |
10096 | Even the elements of sets in ZFC are sets, resting on the pure empty set [George/Velleman] |
10097 | Axiom of Extensionality: for all sets x and y, if x and y have the same elements then x = y [George/Velleman] |
10100 | Axiom of Pairing: for all sets x and y, there is a set z containing just x and y [George/Velleman] |
17900 | The Axiom of Reducibility made impredicative definitions possible [George/Velleman] |
10109 | ZFC can prove that there is no set corresponding to the concept 'set' [George/Velleman] |
10108 | As a reduction of arithmetic, set theory is not fully general, and so not logical [George/Velleman] |
6858 | Formal logic struck me as exactly the language I wanted to think in [Williamson] |
21611 | Formal semantics defines validity as truth preserved in every model [Williamson] |
21606 | 'Bivalence' is the meta-linguistic principle that 'A' in the object language is true or false [Williamson] |
21605 | Excluded Middle is 'A or not A' in the object language [Williamson] |
10111 | Asserting Excluded Middle is a hallmark of realism about the natural world [George/Velleman] |
18492 | Not all quantification is either objectual or substitutional [Williamson] |
15136 | Substitutional quantification is metaphysical neutral, and equivalent to a disjunction of instances [Williamson] |
15138 | Not all quantification is objectual or substitutional [Williamson] |
21612 | Or-elimination is 'Argument by Cases'; it shows how to derive C from 'A or B' [Williamson] |
10129 | A 'model' is a meaning-assignment which makes all the axioms true [George/Velleman] |
10105 | Differences between isomorphic structures seem unimportant [George/Velleman] |
10119 | Consistency is a purely syntactic property, unlike the semantic property of soundness [George/Velleman] |
10126 | A 'consistent' theory cannot contain both a sentence and its negation [George/Velleman] |
10120 | Soundness is a semantic property, unlike the purely syntactic property of consistency [George/Velleman] |
10127 | A 'complete' theory contains either any sentence or its negation [George/Velleman] |
21599 | A sorites stops when it collides with an opposite sorites [Williamson] |
10106 | Rational numbers give answers to division problems with integers [George/Velleman] |
10102 | The integers are answers to subtraction problems involving natural numbers [George/Velleman] |
10107 | Real numbers provide answers to square root problems [George/Velleman] |
9946 | Logicists say mathematics is applicable because it is totally general [George/Velleman] |
10125 | The classical mathematician believes the real numbers form an actual set [George/Velleman] |
17899 | Second-order induction is stronger as it covers all concepts, not just first-order definable ones [George/Velleman] |
10128 | The Incompleteness proofs use arithmetic to talk about formal arithmetic [George/Velleman] |
17902 | A successor is the union of a set with its singleton [George/Velleman] |
10133 | Frege's Theorem shows the Peano Postulates can be derived from Hume's Principle [George/Velleman] |
10130 | Set theory can prove the Peano Postulates [George/Velleman] |
9183 | Platonism claims that some true assertions have singular terms denoting abstractions, so abstractions exist [Williamson] |
10089 | Talk of 'abstract entities' is more a label for the problem than a solution to it [George/Velleman] |
10131 | If mathematics is not about particulars, observing particulars must be irrelevant [George/Velleman] |
10092 | In the unramified theory of types, the types are objects, then sets of objects, sets of sets etc. [George/Velleman] |
10094 | The theory of types seems to rule out harmless sets as well as paradoxical ones. [George/Velleman] |
10095 | Type theory has only finitely many items at each level, which is a problem for mathematics [George/Velleman] |
17901 | Type theory prohibits (oddly) a set containing an individual and a set of individuals [George/Velleman] |
10114 | Bounded quantification is originally finitary, as conjunctions and disjunctions [George/Velleman] |
10134 | Much infinite mathematics can still be justified finitely [George/Velleman] |
10123 | The intuitionists are the idealists of mathematics [George/Velleman] |
10124 | Gödel's First Theorem suggests there are truths which are independent of proof [George/Velleman] |
9601 | The realist/anti-realist debate is notoriously obscure and fruitless [Williamson] |
15137 | If 'fact' is a noun, can we name the fact that dogs bark 'Mary'? [Williamson] |
21589 | When bivalence is rejected because of vagueness, we lose classical logic [Williamson] |
21596 | Vagueness undermines the stable references needed by logic [Williamson] |
21601 | A vague term can refer to very precise elements [Williamson] |
21629 | Equally fuzzy objects can be identical, so fuzziness doesn't entail vagueness [Williamson] |
9599 | There cannot be vague objects, so there may be no such thing as a mountain [Williamson] |
21591 | Vagueness is epistemic. Statements are true or false, but we often don't know which [Williamson] |
21619 | If a heap has a real boundary, omniscient speakers would agree where it is [Williamson] |
21620 | The epistemic view says that the essence of vagueness is ignorance [Williamson] |
21622 | If there is a true borderline of which we are ignorant, this drives a wedge between meaning and use [Williamson] |
9120 | Vagueness in a concept is its indiscriminability from other possible concepts [Williamson] |
6863 | Close to conceptual boundaries judgement is too unreliable to give knowledge [Williamson] |
21625 | The vagueness of 'heap' can remain even when the context is fixed [Williamson] |
21614 | The 'nihilist' view of vagueness says that 'heap' is not a legitimate concept [Williamson] |
21617 | We can say propositions are bivalent, but vague utterances don't express a proposition [Williamson] |
21618 | If the vague 'TW is thin' says nothing, what does 'TW is thin if his perfect twin is thin' say? [Williamson] |
21590 | Asking when someone is 'clearly' old is higher-order vagueness [Williamson] |
21592 | Supervaluation keeps classical logic, but changes the truth in classical semantics [Williamson] |
21603 | You can't give a precise description of a language which is intrinsically vague [Williamson] |
21604 | Supervaluation assigns truth when all the facts are respected [Williamson] |
21607 | Supervaluation has excluded middle but not bivalence; 'A or not-A' is true, even when A is undecided [Williamson] |
21608 | Truth-functionality for compound statements fails in supervaluation [Williamson] |
21609 | Supervaluationism defines 'supertruth', but neglects it when defining 'valid' [Williamson] |
21610 | Supervaluation adds a 'definitely' operator to classical logic [Williamson] |
21613 | Supervaluationism cannot eliminate higher-order vagueness [Williamson] |
21633 | Nominalists suspect that properties etc are our projections, and could have been different [Williamson] |
6861 | What sort of logic is needed for vague concepts, and what sort of concept of truth? [Williamson] |
9602 | Common sense and classical logic are often simultaneously abandoned in debates on vagueness [Williamson] |
21630 | If fuzzy edges are fine, then why not fuzzy temporal, modal or mereological boundaries? [Williamson] |
21632 | A river is not just event; it needs actual and counterfactual boundaries [Williamson] |
14625 | Necessity is counterfactually implied by its negation; possibility does not counterfactually imply its negation [Williamson] |
14623 | Strict conditionals imply counterfactual conditionals: □(A⊃B)⊃(A□→B) [Williamson] |
14624 | Counterfactual conditionals transmit possibility: (A□→B)⊃(◊A⊃◊B) [Williamson] |
14531 | Rather than define counterfactuals using necessity, maybe necessity is a special case of counterfactuals [Williamson, by Hale/Hoffmann,A] |
21621 | We can't infer metaphysical necessities to be a priori knowable - or indeed knowable in any way [Williamson] |
9598 | Modal thinking isn't a special intuition; it is part of ordinary counterfactual thinking [Williamson] |
16536 | Williamson can't base metaphysical necessity on the psychology of causal counterfactuals [Lowe on Williamson] |
9596 | We scorn imagination as a test of possibility, forgetting its role in counterfactuals [Williamson] |
15142 | Our ability to count objects across possibilities favours the Barcan formulas [Williamson] |
18925 | If talking donkeys are possible, something exists which could be a talking donkey [Williamson, by Cameron] |
21627 | We have inexact knowledge when we include margins of error [Williamson] |
4760 | Belief aims at knowledge (rather than truth), and mere believing is a kind of botched knowing [Williamson] |
19527 | We don't acquire evidence and then derive some knowledge, because evidence IS knowledge [Williamson] |
19512 | Don't analyse knowledge; use knowledge to analyse other concepts in epistemology [Williamson, by DeRose] |
19528 | Knowledge is prior to believing, just as doing is prior to trying to do [Williamson] |
19529 | Belief explains justification, and knowledge explains belief, so knowledge explains justification [Williamson] |
19530 | A neutral state of experience, between error and knowledge, is not basic; the successful state is basic [Williamson] |
19531 | Internalism about mind is an obsolete view, and knowledge-first epistemology develops externalism [Williamson] |
19536 | Knowledge-first says your total evidence IS your knowledge [Williamson] |
19526 | Surely I am acquainted with physical objects, not with appearances? [Williamson] |
9597 | There are 'armchair' truths which are not a priori, because experience was involved [Williamson] |
6860 | How can one discriminate yellow from red, but not the colours in between? [Williamson] |
9592 | Intuition is neither powerful nor vacuous, but reveals linguistic or conceptual competence [Williamson] |
20181 | When analytic philosophers run out of arguments, they present intuitions as their evidence [Williamson] |
21626 | Knowing you know (KK) is usually denied if the knowledge concept is missing, or not considered [Williamson] |
14628 | Imagination is important, in evaluating possibility and necessity, via counterfactuals [Williamson] |
21631 | To know, believe, hope or fear, one must grasp the thought, but not when you fail to do them [Williamson] |
10110 | Corresponding to every concept there is a class (some of them sets) [George/Velleman] |
21600 | 'Blue' is not a family resemblance, because all the blues resemble in some respect [Williamson] |
9595 | You might know that the word 'gob' meant 'mouth', but not be competent to use it [Williamson] |
21615 | References to the 'greatest prime number' have no reference, but are meaningful [Williamson] |
18038 | The 't' and 'f' of formal semantics has no philosophical interest, and may not refer to true and false [Williamson] |
19534 | How does inferentialism distinguish the patterns of inference that are essential to meaning? [Williamson] |
19535 | Internalist inferentialism has trouble explaining how meaning and reference relate [Williamson] |
19533 | Inferentialist semantics relies on internal inference relations, not on external references [Williamson] |
19532 | Truth-conditional referential semantics is externalist, referring to worldly items [Williamson] |
21624 | It is known that there is a cognitive loss in identifying propositions with possible worlds [Williamson] |
19216 | Propositions (such as 'that dog is barking') only exist if their items exist [Williamson] |
6017 | Nomos is king [Pindar] |
9600 | If languages are intertranslatable, and cognition is innate, then cultures are all similar [Williamson] |
15133 | A thing can't be the only necessary existent, because its singleton set would be as well [Williamson] |