96 ideas
| 15784 | The Razor seems irrelevant for Meinongians, who allow absolutely everything to exist [Lycan] |
| 15787 | Maybe Ockham's Razor is a purely aesthetic principle [Lycan] |
| 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] |
| 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] |
| 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] |
| 9517 | The 'scope' of a connective is the connective, the linked formulae, and the brackets [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] |
| 6548 | Physicalism requires the naturalisation or rejection of set theory [Lycan] |
| 9520 | The paradoxes of material implication are P |- Q → P, and ¬P |- P → Q [Lemmon] |
| 7755 | Singular terms refer, using proper names, definite descriptions, singular personal pronouns, demonstratives, etc. [Lycan] |
| 6531 | Institutions are not reducible as types, but they are as tokens [Lycan] |
| 6532 | Types cannot be reduced, but levels of reduction are varied groupings of the same tokens [Lycan] |
| 6534 | One location may contain molecules, a metal strip, a key, an opener of doors, and a human tragedy [Lycan] |
| 5500 | Biologists see many organic levels, 'abstract' if seen from below, 'structural' if seen from above [Lycan] |
| 6529 | I see the 'role'/'occupant' distinction as fundamental to metaphysics [Lycan] |
| 15792 | Maybe non-existent objects are sets of properties [Lycan] |
| 5494 | 'Lightning is electric discharge' and 'Phosphorus is Venus' are synthetic a posteriori identities [Lycan] |
| 15795 | Treating possible worlds as mental needs more actual mental events [Lycan] |
| 15796 | Possible worlds must be made of intensional objects like propositions or properties [Lycan] |
| 15794 | If 'worlds' are sentences, and possibility their consistency, consistency may rely on possibility [Lycan] |
| 6549 | I think greenness is a complex microphysical property of green objects [Lycan] |
| 6543 | Intentionality comes in degrees [Lycan] |
| 6537 | Teleological views allow for false intentional content, unlike causal and nomological theories [Lycan] |
| 6546 | Pain is composed of urges, desires, impulses etc, at different levels of abstraction [Lycan] |
| 6547 | The right 'level' for qualia is uncertain, though top (behaviourism) and bottom (particles) are false [Lycan] |
| 6527 | If energy in the brain disappears into thin air, this breaches physical conservation laws [Lycan] |
| 6528 | In lower animals, psychology is continuous with chemistry, and humans are continuous with animals [Lycan] |
| 6554 | Two behaviourists meet. The first says,"You're fine; how am I?" [Lycan] |
| 6541 | Functionalism must not be too abstract to allow inverted spectrum, or so structural that it becomes chauvinistic [Lycan] |
| 6545 | If functionalism focuses on folk psychology, it ignores lower levels of function [Lycan] |
| 5496 | Functionalism has three linked levels: physical, functional, and mental [Lycan] |
| 6539 | The distinction between software and hardware is not clear in computing [Lycan] |
| 6535 | Teleological characterisations shade off smoothly into brutely physical ones [Lycan] |
| 6533 | Mental types are a subclass of teleological types at a high level of functional abstraction [Lycan] |
| 5499 | A mental state is a functional realisation of a brain state when it serves the purpose of the organism [Lycan] |
| 6544 | Identity theory is functionalism, but located at the lowest level of abstraction [Lycan] |
| 6530 | We reduce the mind through homuncular groups, described abstractly by purpose [Lycan] |
| 6536 | Teleological functionalism helps us to understand psycho-biological laws [Lycan] |
| 6542 | A Martian may exhibit human-like behaviour while having very different sensations [Lycan] |
| 7768 | The truth conditions theory sees meaning as representation [Lycan] |
| 7766 | Meaning must be known before we can consider verification [Lycan] |
| 7763 | It is hard to state a rule of use for a proper name [Lycan] |
| 7764 | Could I successfully use an expression, without actually understanding it? [Lycan] |
| 7770 | Truth conditions will come out the same for sentences with 'renate' or 'cordate' [Lycan] |
| 7773 | A sentence's truth conditions is the set of possible worlds in which the sentence is true [Lycan] |
| 7774 | Possible worlds explain aspects of meaning neatly - entailment, for example, is the subset relation [Lycan] |
| 6005 | Animals are dangerous and nourishing, and can't form contracts of justice [Hermarchus, by Sedley] |
| 6538 | We need a notion of teleology that comes in degrees [Lycan] |
| 5501 | People are trying to explain biological teleology in naturalistic causal terms [Lycan] |
| 6551 | 'Physical' means either figuring in physics descriptions, or just located in space-time [Lycan] |