91 ideas
| 6200 | Wisdom is knowing the highest good, and conforming the will to it [Kant] |
| 6207 | What fills me with awe are the starry heavens above me and the moral law within me [Kant] |
| 6184 | Consistency is the highest obligation of a philosopher [Kant] |
| 6203 | Metaphysics is just a priori universal principles of physics [Kant] |
| 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] |
| 6181 | Necessity cannot be extracted from an empirical proposition [Kant] |
| 15473 | How does anything get outside itself? [Fodor, by Martin,CB] |
| 2981 | Is intentionality outwardly folk psychology, inwardly mentalese? [Lyons on Fodor] |
| 2985 | Are beliefs brains states, but picked out at a "higher level"? [Lyons on Fodor] |
| 3135 | Is thought a syntactic computation using representations? [Fodor, by Rey] |
| 2983 | Maybe narrow content is physical, broad content less so [Lyons on Fodor] |
| 6183 | Can pure reason determine the will, or are empirical conditions relevant? [Kant] |
| 6191 | The will is the faculty of purposes, which guide desires according to principles [Kant] |
| 6190 | The sole objects of practical reason are the good and the evil [Kant] |
| 18235 | Only human reason can confer value on our choices [Kant, by Korsgaard] |
| 6196 | People cannot come to morality through feeling, because morality must not be sensuous [Kant] |
| 18675 | Kant may rate two things as finally valuable: having a good will, and deserving happiness [Orsi on Kant] |
| 22007 | An autonomous agent has dignity [Würde], which has absolute worth [Kant, by Pinkard] |
| 18234 | The good will is unconditionally good, because it is the only possible source of value [Kant, by Korsgaard] |
| 6192 | Good or evil cannot be a thing, but only a maxim of action, making the person good or evil [Kant] |
| 6197 | Morality involves duty and respect for law, not love of the outcome [Kant] |
| 6193 | Our happiness is all that matters, not as a sensation, but as satisfaction with our whole existence [Kant] |
| 1452 | Happiness is the condition of a rational being for whom everything goes as they wish [Kant] |
| 1454 | Morality is not about making ourselves happy, but about being worthy of happiness [Kant] |
| 6194 | The highest worth for human beings lies in dispositions, not just actions [Kant] |
| 6198 | Virtue is the supreme state of our pursuit of happiness, and so is supreme good [Kant] |
| 1456 | Moral law is holy, and the best we can do is achieve virtue through respect for the law [Kant] |
| 6185 | No one would lend money unless a universal law made it secure, even after death [Kant] |
| 6187 | Universality determines the will, and hence extends self-love into altruism [Kant] |
| 6201 | Everyone (even God) must treat rational beings as ends in themselves, and not just as means [Kant] |
| 6186 | A holy will is incapable of any maxims which conflict with the moral law [Kant] |
| 6195 | Reason cannot solve the problem of why a law should motivate the will [Kant] |
| 6188 | A permanent natural order could not universalise a rule permitting suicide [Kant] |
| 6199 | Obligation does not rest on the existence of God, but on the autonomy of reason [Kant] |
| 1453 | We have to postulate something outside nature which makes happiness coincide with morality [Kant] |
| 1455 | Belief in justice requires belief in a place for justice (heaven), a time (eternity), and a cause (God) [Kant, by PG] |
| 6205 | To know if this world must have been created by God, we would need to know all other possible worlds [Kant] |
| 6204 | Using God to explain nature is referring to something inconceivable to explain what is in front of you [Kant] |
| 6206 | From our limited knowledge we can infer great virtues in God, but not ultimate ones [Kant] |
| 6202 | In all naturalistic concepts of God, if you remove the human qualities there is nothing left [Kant] |