90 ideas
9535 | 'Contradictory' propositions always differ in truth-value [Lemmon] |
9512 | We write the 'negation' of P (not-P) as ¬ [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] |
9514 | If A and B are 'interderivable' from one another we may write A -||- B [Lemmon] |
9508 | The sign |- may be read as 'therefore' [Lemmon] |
9509 | That proposition that both P and Q is their 'conjunction', 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] |
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] |
9516 | A 'well-formed formula' follows the rules for variables, ¬, →, ∧, ∨, and ↔ [Lemmon] |
9518 | A 'theorem' is the conclusion of a provable sequent with zero assumptions [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] |
9517 | The 'scope' of a connective is the connective, the linked formulae, and the brackets [Lemmon] |
9529 | A wff is 'inconsistent' if all assignments to variables result in the value F [Lemmon] |
9519 | A 'substitution-instance' is a wff formed by consistent replacing variables with wffs [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] |
9397 | CP: Given a proof of B from A as assumption, we may derive A→B [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] |
9401 | ∨E: Derive C from A∨B, if C can be derived both from A and from B [Lemmon] |
9398 | ∧I: Given A and B, we may derive A∧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] |
9396 | DN: Given A, we may derive ¬¬A [Lemmon] |
9394 | MPP: Given A and A→B, we may derive B [Lemmon] |
9400 | ∨I: Given either A or B separately, we may derive A∨B [Lemmon] |
9522 | 'Modus ponendo tollens' (MPT) says P, ¬(P ∧ Q) |- ¬Q [Lemmon] |
9521 | 'Modus tollendo ponens' (MTP) 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] |
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] |
9520 | The paradoxes of material implication are P |- Q → P, and ¬P |- P → Q [Lemmon] |
13065 | Understanding is an extremely vague concept [Salmon] |
13047 | It is knowing 'why' that gives scientific understanding, not knowing 'that' [Salmon] |
13054 | Correlations can provide predictions, but only causes can give explanations [Salmon] |
22189 | Why abandon a theory if you don't have a better one? [Gorham] |
22190 | If a theory is more informative it is less probable [Gorham] |
22192 | Is Newton simpler with universal simultaneity, or Einstein simpler without absolute time? [Gorham] |
22194 | Structural Realism says mathematical structures persist after theory rejection [Gorham] |
22195 | Structural Realists must show the mathematics is both crucial and separate [Gorham] |
13067 | For the instrumentalists there are no scientific explanations [Salmon] |
22196 | For most scientists their concepts are not just useful, but are meant to be true and accurate [Gorham] |
22197 | Theories aren't just for organising present experience if they concern the past or future [Gorham] |
13055 | Good induction needs 'total evidence' - the absence at the time of any undermining evidence [Salmon] |
13046 | Scientific explanation is not reducing the unfamiliar to the familiar [Salmon] |
13058 | Why-questions can seek evidence as well as explanation [Salmon] |
14366 | An explanation is a table of statistical information [Salmon, by Strevens] |
13050 | The 'inferential' conception is that all scientific explanations are arguments [Salmon] |
13059 | Ontic explanations can be facts, or reports of facts [Salmon] |
13064 | The three basic conceptions of scientific explanation are modal, epistemic, and ontic [Salmon] |
22193 | Consilience makes the component sciences more likely [Gorham] |
13049 | We must distinguish true laws because they (unlike accidental generalizations) explain things [Salmon] |
13051 | Deductive-nomological explanations will predict, and their predictions will explain [Salmon] |
13053 | A law is not enough for explanation - we need information about what makes a difference [Salmon] |
13061 | Flagpoles explain shadows, and not vice versa, because of temporal ordering [Salmon] |
17093 | Causation produces productive mechanisms; to understand the world, understand these mechanisms [Salmon] |
17492 | Salmon's interaction mechanisms needn't be regular, or involving any systems [Glennan on Salmon] |
13045 | Explanation at the quantum level will probably be by entirely new mechanisms [Salmon] |
13062 | Does an item have a function the first time it occurs? [Salmon] |
13063 | Explanations reveal the mechanisms which produce the facts [Salmon] |
16557 | Salmon's mechanisms are processes and interactions, involving marks, or conserved quantities [Salmon, by Machamer/Darden/Craver] |
13060 | Can events whose probabilities are low be explained? [Salmon] |
13056 | Statistical explanation needs relevance, not high probability [Salmon] |
13057 | Think of probabilities in terms of propensities rather than frequencies [Salmon] |
22198 | Aristotelian physics has circular celestial motion and linear earthly motion [Gorham] |
8412 | A causal interaction is when two processes intersect, and correlated modifications persist afterwards [Salmon] |
8413 | Cause must come first in propagations of causal interactions, but interactions are simultaneous [Salmon] |
8411 | Instead of localised events, I take enduring and extended processes as basic to causation [Salmon] |
4784 | Salmon says processes rather than events should be basic in a theory of physical causation [Salmon, by Psillos] |
8409 | Probabilistic causal concepts are widely used in everyday life and in science [Salmon] |