143 ideas
| 16395 | Kripke separated semantics from metaphysics, rather than linking them, making the latter independent [Kripke, by Stalnaker] |
| 17034 | Analyses of concepts using entirely different terms are very inclined to fail [Kripke] |
| 4955 | Some definitions aim to fix a reference rather than give a meaning [Kripke] |
| 9535 | 'Contradictory' propositions always differ in truth-value [Lemmon] |
| 9509 | That proposition that both P and Q is their 'conjunction', written P∧Q [Lemmon] |
| 9508 | The sign |- may be read as 'therefore' [Lemmon] |
| 9514 | If A and B are 'interderivable' from one another we may write A -||- B [Lemmon] |
| 9511 | We write the conditional 'if P (antecedent) then Q (consequent)' as P→Q [Lemmon] |
| 9512 | We write the 'negation' of P (not-P) as ¬ [Lemmon] |
| 9510 | That proposition that either P or Q is their 'disjunction', written P∨Q [Lemmon] |
| 9513 | We write 'P if and only if Q' as P↔Q; it is also P iff Q, or (P→Q)∧(Q→P) [Lemmon] |
| 9516 | A 'well-formed formula' follows the rules for variables, ¬, →, ∧, ∨, and ↔ [Lemmon] |
| 9519 | A 'substitution-instance' is a wff formed by consistent replacing variables with wffs [Lemmon] |
| 9529 | A wff is 'inconsistent' if all assignments to variables result in the value F [Lemmon] |
| 9534 | Two propositions are 'equivalent' if they mirror one another's truth-value [Lemmon] |
| 9517 | The 'scope' of a connective is the connective, the linked formulae, and the brackets [Lemmon] |
| 9518 | A 'theorem' is the conclusion of a provable sequent with zero assumptions [Lemmon] |
| 9533 | A 'implies' B if B is true whenever A is true (so that A→B is tautologous) [Lemmon] |
| 9532 | 'Subcontrary' propositions are never both false, so that A∨B is a tautology [Lemmon] |
| 9531 | 'Contrary' propositions are never both true, so that ¬(A∧B) is a tautology [Lemmon] |
| 9528 | A wff is a 'tautology' if all assignments to variables result in the value T [Lemmon] |
| 9530 | A wff is 'contingent' if produces at least one T and at least one F [Lemmon] |
| 9396 | DN: Given A, we may derive ¬¬A [Lemmon] |
| 9398 | ∧I: Given A and B, we may derive A∧B [Lemmon] |
| 9394 | MPP: Given A and A→B, we may derive B [Lemmon] |
| 9399 | ∧E: Given A∧B, we may derive either A or B separately [Lemmon] |
| 9401 | ∨E: Derive C from A∨B, if C can be derived both from A and from B [Lemmon] |
| 9395 | MTT: Given ¬B and A→B, we derive ¬A [Lemmon] |
| 9393 | A: we may assume any proposition at any stage [Lemmon] |
| 9400 | ∨I: Given either A or B separately, we may derive A∨B [Lemmon] |
| 9402 | RAA: If assuming A will prove B∧¬B, then derive ¬A [Lemmon] |
| 9397 | CP: Given a proof of B from A as assumption, we may derive A→B [Lemmon] |
| 9522 | 'Modus ponendo tollens' (MPT) says P, ¬(P ∧ Q) |- ¬Q [Lemmon] |
| 9526 | We can change conjunctions into negated conditionals with P→Q -||- ¬(P → ¬Q) [Lemmon] |
| 9527 | The Distributive Laws can rearrange a pair of conjunctions or disjunctions [Lemmon] |
| 9523 | De Morgan's Laws make negated conjunctions/disjunctions into non-negated disjunctions/conjunctions [Lemmon] |
| 9524 | We can change conditionals into disjunctions with P→Q -||- ¬P ∨ Q [Lemmon] |
| 9525 | We can change conditionals into negated conjunctions with P→Q -||- ¬(P ∧ ¬Q) [Lemmon] |
| 9521 | 'Modus tollendo ponens' (MTP) says ¬P, P ∨ Q |- Q [Lemmon] |
| 9537 | Truth-tables are good for showing invalidity [Lemmon] |
| 9538 | A truth-table test is entirely mechanical, but this won't work for more complex logic [Lemmon] |
| 9536 | If any of the nine rules of propositional logic are applied to tautologies, the result is a tautology [Lemmon] |
| 9539 | Propositional logic is complete, since all of its tautologous sequents are derivable [Lemmon] |
| 13909 | Write '(∀x)(...)' to mean 'take any x: then...', and '(∃x)(...)' to mean 'there is an x such that....' [Lemmon] |
| 13902 | 'Gm' says m has property G, and 'Pmn' says m has relation P to n [Lemmon] |
| 13911 | The 'symbols' are bracket, connective, term, variable, predicate letter, reverse-E [Lemmon] |
| 13910 | Our notation uses 'predicate-letters' (for 'properties'), 'variables', 'proper names', 'connectives' and 'quantifiers' [Lemmon] |
| 13904 | Universal Elimination (UE) lets us infer that an object has F, from all things having F [Lemmon] |
| 13901 | Predicate logic uses propositional connectives and variables, plus new introduction and elimination rules [Lemmon] |
| 13903 | Universal elimination if you start with the universal, introduction if you want to end with it [Lemmon] |
| 13906 | With finite named objects, we can generalise with &-Intro, but otherwise we need ∀-Intro [Lemmon] |
| 13908 | UE all-to-one; UI one-to-all; EI arbitrary-to-one; EE proof-to-one [Lemmon] |
| 13905 | If there is a finite domain and all objects have names, complex conjunctions can replace universal quantifiers [Lemmon] |
| 13900 | 'Some Frenchmen are generous' is rendered by (∃x)(Fx→Gx), and not with the conditional → [Lemmon] |
| 10559 | Kripke's modal semantics presupposes certain facts about possible worlds [Kripke, by Zalta] |
| 9520 | The paradoxes of material implication are P |- Q → P, and ¬P |- P → Q [Lemmon] |
| 10437 | Names are rigid, making them unlike definite descriptions [Kripke, by Sainsbury] |
| 4949 | Names are rigid designators, which designate the same object in all possible worlds [Kripke] |
| 4951 | A bundle of qualities is a collection of abstractions, so it can't be a particular [Kripke] |
| 17031 | A name can still refer even if it satisfies none of its well-known descriptions [Kripke] |
| 8957 | Some references, such as 'Neptune', have to be fixed by description rather than baptism [Kripke, by Szabó] |
| 10428 | Proper names must have referents, because they are not descriptive [Kripke, by Sainsbury] |
| 4959 | A name's reference is not fixed by any marks or properties of the referent [Kripke] |
| 14896 | Kripke's metaphysics (essences, kinds, rigidity) blocks the slide into sociology [Kripke, by Ladyman/Ross] |
| 17647 | Kripke individuates objects by essential modal properties (and presupposes essentialism) [Kripke, by Putnam] |
| 16995 | Given that a table is made of molecules, could it not be molecular and still be this table? [Kripke] |
| 17047 | If we imagine this table made of ice or different wood, we are imagining a different table [Kripke] |
| 5450 | For Kripke, essence is origin; for Putnam, essence is properties; for Wiggins, essence is membership of a kind [Kripke, by Mautner] |
| 17055 | Atomic number 79 is part of the nature of the gold we know [Kripke] |
| 16997 | An essential property is true of an object in any case where it would have existed [Kripke] |
| 17045 | De re modality is an object having essential properties [Kripke] |
| 17030 | Important properties of an object need not be essential to it [Kripke] |
| 16955 | Kripke says internal structure fixes species; I say it is genetic affinity and a common descent [Kripke, by Dummett] |
| 16996 | Given that Nixon is indeed a human being, that he might not have been does not concern knowledge [Kripke] |
| 13971 | Kripke claims that some properties, only knowable posteriori, are known a priori to be essential [Kripke, by Soames] |
| 12100 | An essence is the necessary properties, derived from an intuitive identity, in origin, type and material [Kripke, by Witt] |
| 16991 | No one seems to know the identity conditions for a material object (or for people) over time [Kripke] |
| 11867 | If we lose track of origin, how do we show we are maintaining a reference? [Kripke, by Wiggins] |
| 12018 | Kripke argues, of the Queen, that parents of an organism are essentially so [Kripke, by Forbes,G] |
| 17046 | Could the actual Queen have been born of different parents? [Kripke] |
| 8274 | Socrates can't have a necessary origin, because he might have had no 'origin' [Lowe on Kripke] |
| 17036 | Identity statements can be contingent if they rely on descriptions [Kripke] |
| 17038 | If Hesperus and Phosophorus are the same, they can't possibly be different [Kripke] |
| 11880 | Kripke says his necessary a posteriori examples are known a priori to be necessary [Kripke, by Mackie,P] |
| 4797 | Instead of being regularities, maybe natural laws are the weak a posteriori necessities of Kripke [Kripke, by Psillos] |
| 17037 | Physical necessity may be necessity in the highest degree [Kripke] |
| 4728 | Kripke separates necessary and a priori, proposing necessary a posteriori and contingent a priori examples [Kripke, by O'Grady] |
| 16990 | A priori = Necessary because we imagine all worlds, and we know without looking at actuality? [Kripke] |
| 9386 | The meter is defined necessarily, but the stick being one meter long is contingent a priori [Kripke] |
| 2408 | Kripke has demonstrated that some necessary truths are only knowable a posteriori [Kripke, by Chalmers] |
| 4960 | "'Hesperus' is 'Phosphorus'" is necessarily true, if it is true, but not known a priori [Kripke] |
| 4966 | Theoretical identities are between rigid designators, and so are necessary a posteriori [Kripke] |
| 13967 | Kripke's essentialist necessary a posteriori opened the gap between conceivable and really possible [Soames on Kripke] |
| 13970 | Kripke gets to the necessary a posteriori by only allowing conceivability when combined with actuality [Kripke, by Soames] |
| 16992 | Possible worlds aren't puzzling places to learn about, but places we ourselves describe [Kripke] |
| 16993 | If we discuss what might have happened to Nixon, we stipulate that it is about Nixon [Kripke] |
| 16998 | Transworld identification is unproblematic, because we stipulate that we rigidly refer to something [Kripke] |
| 17001 | A table in some possible world should not even be identified by its essential properties [Kripke] |
| 4952 | Identification across possible worlds does not need properties, even essential ones [Kripke] |
| 7761 | Test for rigidity by inserting into the sentence 'N might not have been N' [Kripke, by Lycan] |
| 7693 | Kripke avoids difficulties of transworld identity by saying it is a decision, not a discovery [Kripke, by Jacquette] |
| 5821 | Saying that natural kinds are 'rigid designators' is the same as saying they are 'indexical' [Kripke, by Putnam] |
| 14068 | If Kripke names must still denote a thing in a non-actual situation, the statue isn't its clay [Gibbard on Kripke] |
| 10436 | A rigid expression may refer at a world to an object not existing in that world [Kripke, by Sainsbury] |
| 4953 | We do not begin with possible worlds and place objects in them; we begin with objects in the real world [Kripke] |
| 4961 | It is a necessary truth that Elizabeth II was the child of two particular parents [Kripke] |
| 16986 | That there might have been unicorns is false; we don't know the circumstances for unicorns [Kripke] |
| 8259 | Kripke has breathed new life into the a priori/a posteriori distinction [Kripke, by Lowe] |
| 16989 | Rather than 'a priori truth', it is best to stick to whether some person knows it on a priori evidence [Kripke] |
| 4947 | A priori truths can be known independently of experience - but they don't have to be [Kripke] |
| 13975 | Kripke was more successful in illuminating necessity than a priority (and their relations to analyticity) [Kripke, by Soames] |
| 17048 | Analytic judgements are a priori, even when their content is empirical [Kripke] |
| 4948 | Intuition is the strongest possible evidence one can have about anything [Kripke] |
| 4958 | Identities like 'heat is molecule motion' are necessary (in the highest degree), not contingent [Kripke] |
| 4967 | It seems logically possible to have the pain brain state without the actual pain [Kripke] |
| 7430 | Kripke assumes that mind-brain identity designates rigidly, which it doesn't [Armstrong on Kripke] |
| 7867 | If consciousness could separate from brain, then it cannot be identical with brain [Kripke, by Papineau] |
| 3228 | Kripke says pain is necessarily pain, but a brain state isn't necessarily painful [Kripke, by Rey] |
| 5832 | Identity must be necessary, but pain isn't necessarily a brain state, so they aren't identical [Kripke, by Schwartz,SP] |
| 4968 | Identity theorists seem committed to no-brain-event-no-pain, and vice versa, which seems wrong [Kripke] |
| 16394 | Kripke derives accounts of reference and proper names from assumptions about worlds and essences [Stalnaker on Kripke] |
| 17874 | Kripke has a definitional account of kinds, but not of naming [Almog on Kripke] |
| 5822 | The important cause is not between dubbing and current use, but between the item and the speaker's information [Evans on Kripke] |
| 17033 | We may refer through a causal chain, but still change what is referred to [Kripke] |
| 4689 | Kripke makes reference a largely social matter, external to the mind of the speaker [Kripke, by McGinn] |
| 17504 | Kripke's theory is important because it gives a collective account of reference [Kripke, by Putnam] |
| 17035 | We refer through the community, going back to the original referent [Kripke] |
| 16988 | Descriptive reference shows how to refer, how to identify two things, and how to challenge existence [Kripke, by PG] |
| 17029 | It can't be necessary that Aristotle had the properties commonly attributed to him [Kripke] |
| 14893 | Rigid designation creates a puzzle - why do some necessary truths appear to be contingent? [Kripke, by Macià/Garcia-Carpentiro] |
| 5996 | Critolaus redefined Aristotle's moral aim as fulfilment instead of happiness [Critolaus, by White,SA] |
| 4963 | The properties that fix reference are contingent, the properties involving meaning are necessary [Kripke] |
| 17056 | Terms for natural kinds are very close to proper names [Kripke] |
| 17053 | Gold's atomic number might not be 79, but if it is, could non-79 stuff be gold? [Kripke] |
| 4964 | 'Cats are animals' has turned out to be a necessary truth [Kripke] |
| 6765 | Nominal essence may well be neither necessary nor sufficient for a natural kind [Kripke, by Bird] |
| 9387 | The scientific discovery (if correct) that gold has atomic number 79 is a necessary truth [Kripke] |
| 17054 | Scientific discoveries about gold are necessary truths [Kripke] |
| 17057 | Once we've found that heat is molecular motion, then that's what it is, in all possible worlds [Kripke] |
| 4965 | Science searches basic structures in search of essences [Kripke] |
| 17050 | Tigers may lack all the properties we originally used to identify them [Kripke] |
| 17049 | 'Tiger' designates a species, and merely looking like the species is not enough [Kripke] |
| 17051 | The original concept of 'cat' comes from paradigmatic instances [Kripke] |