111 ideas
| 7113 | Phenomenology assumes that all consciousness is of something [Sartre] |
| 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] |
| 9517 | The 'scope' of a connective is the connective, the linked formulae, and the brackets [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] |
| 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] |
| 9520 | The paradoxes of material implication are P |- Q → P, and ¬P |- P → Q [Lemmon] |
| 22227 | For Sartre there is only being for-itself, or being in-itself (which is beyond experience) [Sartre, by Daigle] |
| 7114 | The consciousness that says 'I think' is not the consciousness that thinks [Sartre] |
| 7112 | The Cogito depends on a second-order experience, of being conscious of consciousness [Sartre] |
| 7119 | Is the Cogito reporting an immediate experience of doubting, or the whole enterprise of doubting? [Sartre] |
| 20743 | Appearances do not hide the essence; appearances are the essence [Sartre] |
| 7125 | A consciousness can conceive of no other consciousness than itself [Sartre] |
| 7122 | We can never, even in principle, grasp other minds, because the Ego is self-conceiving [Sartre] |
| 7108 | The eternal truth of 2+2=4 is what gives unity to the mind which regularly thinks it [Sartre] |
| 24016 | Consciousness always transcends itself [Sartre] |
| 6151 | Sartre says consciousness is just directedness towards external objects [Sartre, by Rowlands] |
| 7111 | Consciousness exists as consciousness of itself [Sartre] |
| 22226 | Since we are a consciousness, Sartre entirely rejected the unconscious mind [Sartre, by Daigle] |
| 7107 | Intentionality defines, transcends and unites consciousness [Sartre] |
| 3847 | Man is nothing else but the sum of his actions [Sartre] |
| 7109 | If you think of '2+2=4' as the content of thought, the self must be united transcendentally [Sartre] |
| 7106 | The Ego is not formally or materially part of consciousness, but is outside in the world [Sartre] |
| 7117 | How could two I's, the reflective and the reflected, communicate with each other? [Sartre] |
| 7123 | Knowing yourself requires an exterior viewpoint, which is necessarily false [Sartre] |
| 22225 | My ego is more intimate to me, but not more certain than other egos [Sartre] |
| 7116 | When we are unreflective (as when chasing a tram) there is no 'I' [Sartre] |
| 7124 | The Ego never appears except when we are not looking for it [Sartre] |
| 7120 | It is theoretically possible that the Ego consists entirely of false memories [Sartre] |
| 7110 | If the 'I' is transcendental, it unnecessarily splits consciousness in two [Sartre] |
| 7115 | Maybe it is the act of reflection that brings 'me' into existence [Sartre] |
| 7121 | The Ego only appears to reflection, so it is cut off from the World [Sartre] |
| 3846 | Man IS freedom [Sartre] |
| 24013 | An emotion and its object form a unity, so emotion is a mode of apprehension [Sartre] |
| 24017 | Emotion is one of our modes of understanding our Being-in-the-World [Sartre] |
| 24014 | Emotions are a sort of bodily incantation which brings a magic to the world [Sartre] |
| 24015 | Emotions makes us believe in and live in a new world [Sartre] |
| 6164 | Sartre rejects mental content, and the idea that the mind has hidden inner features [Sartre, by Rowlands] |
| 7074 | Man is a useless passion [Sartre] |
| 6687 | Man is the desire to be God [Sartre] |
| 3843 | There is no human nature [Sartre] |
| 20762 | There are no values to justify us, and no excuses [Sartre] |
| 3852 | If values depend on us, freedom is the foundation of all values [Sartre] |
| 22228 | Sartre's freedom is not for whimsical action, but taking responsibility for our own values [Sartre, by Daigle] |
| 22233 | Love is the demand to be loved [Sartre] |
| 22725 | When players don't meet again, defection is the best strategy [Axelrod] |
| 22724 | Good strategies avoid conflict, respond to hostility, forgive, and are clear [Axelrod] |
| 20764 | In becoming what we want to be we create what we think man ought to be [Sartre] |
| 3848 | Cowards are responsible for their cowardice [Sartre] |
| 20763 | When my personal freedom becomes involved, I must want freedom for everyone else [Sartre] |
| 22229 | Existentialists says that cowards and heroes make themselves [Sartre] |
| 20755 | Fear concerns the world, but 'anguish' comes from confronting my self [Sartre] |
| 3842 | Existence before essence (or begin with the subjective) [Sartre] |
| 6868 | 'Existence precedes essence' means we have no pre-existing self, but create it through existence [Sartre, by Le Poidevin] |
| 3844 | Existentialism says man is whatever he makes of himself [Sartre] |
| 22232 | Authenticity is taking responsibility for a situation, with all its risks and emotions [Sartre] |
| 20760 | Sincerity is not authenticity, because it only commits to one particular identity [Sartre, by Aho] |
| 22231 | We flee from the anguish of freedom by seeing ourselves objectively, as determined [Sartre] |
| 20754 | It is dishonest to offer passions as an excuse [Sartre] |
| 22230 | Sartre gradually realised that freedom is curtailed by the weight of situation [Sartre, by Daigle] |
| 3851 | If I do not choose, that is still a choice [Sartre] |
| 6571 | When a man must choose between his mother and the Resistance, no theory can help [Sartre, by Fogelin] |
| 20491 | States have a monopoly of legitimate violence [Sartre, by Wolff,J] |
| 21240 | The truth about events always comes from the oppressed and disadvantaged [Sartre, by Bakewell] |
| 3845 | Without God there is no intelligibility or value [Sartre] |