92 ideas
| 7910 | Pursue truth with the urgency of someone whose clothes are on fire [Ashvaghosha] |
| 4588 | There is no such thing as 'science'; there are just many different sciences [Heil] |
| 9535 | 'Contradictory' propositions always differ in truth-value [Lemmon] |
| 9511 | We write the conditional 'if P (antecedent) then Q (consequent)' as P→Q [Lemmon] |
| 9510 | That proposition that either P or Q is their 'disjunction', written P∨Q [Lemmon] |
| 9512 | We write the 'negation' of P (not-P) as ¬ [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] |
| 9514 | If A and B are 'interderivable' from one another we may write A -||- B [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] |
| 9516 | A 'well-formed formula' follows the rules for variables, ¬, →, ∧, ∨, and ↔ [Lemmon] |
| 9517 | The 'scope' of a connective is the connective, the linked formulae, and the brackets [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] |
| 9531 | 'Contrary' propositions are never both true, so that ¬(A∧B) is a tautology [Lemmon] |
| 9534 | Two propositions are 'equivalent' if they mirror one another's truth-value [Lemmon] |
| 9530 | A wff is 'contingent' if produces at least one T and at least one F [Lemmon] |
| 9532 | 'Subcontrary' propositions are never both false, so that A∨B is a tautology [Lemmon] |
| 9533 | A 'implies' B if B is true whenever A is true (so that A→B is tautologous) [Lemmon] |
| 9528 | A wff is a 'tautology' if all assignments to variables result in the value T [Lemmon] |
| 9518 | A 'theorem' is the conclusion of a provable sequent with zero assumptions [Lemmon] |
| 9398 | ∧I: Given A and B, we may derive A∧B [Lemmon] |
| 9397 | CP: Given a proof of B from A as assumption, we may derive A→B [Lemmon] |
| 9394 | MPP: Given A and A→B, we may derive B [Lemmon] |
| 9402 | RAA: If assuming A will prove B∧¬B, then derive ¬A [Lemmon] |
| 9395 | MTT: Given ¬B and A→B, we derive ¬A [Lemmon] |
| 9400 | ∨I: Given either A or B separately, we may derive A∨B [Lemmon] |
| 9401 | ∨E: Derive C from A∨B, if C can be derived both from A and from B [Lemmon] |
| 9396 | DN: Given A, we may derive ¬¬A [Lemmon] |
| 9393 | A: we may assume any proposition at any stage [Lemmon] |
| 9399 | ∧E: Given A∧B, we may derive either A or B separately [Lemmon] |
| 9521 | 'Modus tollendo ponens' (MTP) says ¬P, P ∨ Q |- Q [Lemmon] |
| 9522 | 'Modus ponendo tollens' (MPT) says P, ¬(P ∧ Q) |- ¬Q [Lemmon] |
| 9525 | We can change conditionals into negated conjunctions with P→Q -||- ¬(P ∧ ¬Q) [Lemmon] |
| 9524 | We can change conditionals into disjunctions with P→Q -||- ¬P ∨ Q [Lemmon] |
| 9523 | De Morgan's Laws make negated conjunctions/disjunctions into non-negated disjunctions/conjunctions [Lemmon] |
| 9527 | The Distributive Laws can rearrange a pair of conjunctions or disjunctions [Lemmon] |
| 9526 | We can change conjunctions into negated conditionals with P→Q -||- ¬(P → ¬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] |
| 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] |
| 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] |
| 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] |
| 9520 | The paradoxes of material implication are P |- Q → P, and ¬P |- P → Q [Lemmon] |
| 4616 | A higher level is 'supervenient' if it is determined by lower levels, but has its own natural laws [Heil] |
| 4603 | Functionalists in Fodor's camp usually say that a genuine property is one that figures in some causal laws [Heil] |
| 4617 | A stone does not possess the property of being a stone; its other properties make it a stone [Heil] |
| 4615 | Complex properties are not new properties, they are merely new combinations of properties [Heil] |
| 4612 | Complex properties are just arrangements of simple properties; they do not "emerge" as separate [Heil] |
| 4587 | From the property predicates P and Q, we can get 'P or Q', but it doesn't have to designate another property [Heil] |
| 4611 | The supporters of 'tropes' treat objects as bundles of tropes, when I think objects 'possess' properties [Heil] |
| 4592 | If you can have the boat without its current planks, and the planks with no boat, the planks aren't the boat [Heil] |
| 4586 | You can't embrace the formal apparatus of possible worlds, but reject the ontology [Heil] |
| 4591 | Idealism explains appearances by identifying appearances with reality [Heil] |
| 4610 | Different generations focus on either the quality of mind, or its scientific standing, or the content of thought [Heil] |
| 4618 | If minds are realised materially, it looks as if the material laws will pre-empt any causal role for mind [Heil] |
| 4621 | Whatever exists has qualities, so it is no surprise that states of minds have qualities [Heil] |
| 4623 | Propositional attitudes are not the only intentional states; there is also mental imagery [Heil] |
| 4626 | The widespread externalist view says intentionality has content because of causal links of agent to world [Heil] |
| 4622 | Error must be possible in introspection, because error is possible in all judgements [Heil] |
| 4590 | If causation is just regularities in events, the interaction of mind and body is not a special problem [Heil] |
| 4614 | Disposition is a fundamental feature of reality, since basic particles are capable of endless possible interactions [Heil] |
| 4595 | No mental state entails inevitable behaviour, because other beliefs or desires may intervene [Heil] |
| 4599 | Hearts are material, but functionalism says the property of being a heart is not a material property [Heil] |
| 4624 | If you are a functionalist, there appears to be no room for qualia [Heil] |
| 4601 | Higher-level sciences cannot be reduced, because their concepts mark boundaries invisible at lower levels [Heil] |
| 4602 | Higher-level sciences designate real properties of objects, which are not reducible to lower levels [Heil] |
| 4593 | 'Property dualism' says mind and body are not substances, but distinct families of properties [Heil] |
| 4597 | Early identity theory talked of mind and brain 'processes', but now the focus is properties [Heil] |
| 4609 | It seems contradictory to be asked to believe that we can be eliminativist about beliefs [Heil] |
| 4596 | The appeal of the identity theory is its simplicity, and its solution to the mental causation problem [Heil] |
| 4598 | Functionalists emphasise that mental processes are not to be reduced to what realises them [Heil] |
| 4619 | 'Multiple realisability' needs to clearly distinguish low-level realisers from what is realised [Heil] |
| 4620 | Multiple realisability is not a relation among properties, but an application of predicates to resembling things [Heil] |
| 4594 | A scientist could know everything about the physiology of headaches, but never have had one [Heil] |
| 4625 | Is mental imagery pictorial, or is it propositional? [Heil] |
| 4607 | Folk psychology and neuroscience are no more competitors than cartography and geology are [Heil] |
| 4605 | Truth-conditions correspond to the idea of 'literal meaning' [Heil] |
| 4606 | To understand 'birds warble' and 'tigers growl', you must also understand 'tigers warble' [Heil] |
| 4604 | If propositions are abstract entities, how do human beings interact with them? [Heil] |
| 7909 | The Eightfold Path concerns morality, wisdom, and tranquillity [Ashvaghosha] |
| 7908 | At the end of a saint, he is not located in space, but just ceases to be disturbed [Ashvaghosha] |