170 ideas
| 2845 | Free and great-souled men do not keep asking "what is the use of it?" [Aristotle] |
| 22521 | Our method of inquiry is to examine the smallest parts that make up the whole [Aristotle] |
| 1570 | Human beings, alone of the animals, have logos [Aristotle] |
| 1574 | Reasoning distinguishes what is beneficial, and hence what is right [Aristotle] |
| 2801 | Intelligence which looks ahead is a natural master, while bodily strength is a natural slave [Aristotle] |
| 22529 | Men are natural leaders (apart from the unnatural ones) [Aristotle] |
| 22571 | 'If each is small, so too are all' is in one way false, for the whole composed of all is not small [Aristotle] |
| 9535 | 'Contradictory' propositions always differ in truth-value [Lemmon] |
| 9509 | That proposition that both P and Q is their 'conjunction', written P∧Q [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] |
| 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] |
| 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] |
| 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] |
| 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] |
| 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] |
| 22525 | The whole is prior to its parts, because parts are defined by their role [Aristotle] |
| 22587 | Understanding is the aim of our nature [Aristotle] |
| 22522 | To grasp something, trace it back to its natural origins [Aristotle] |
| 22524 | The nature of each thing is its mature state [Aristotle] |
| 22528 | The nature of all animate things is to have one part which rules it [Aristotle] |
| 22570 | Rhetoric now enables good speakers to become popular leaders [Aristotle] |
| 22574 | A community can lack self-control [Aristotle] |
| 2837 | Nothing contrary to nature is beautiful [Aristotle] |
| 2824 | The collective judgement of many people on art is better than that of an individual [Aristotle] |
| 2846 | Music can mould the character to be virtuous (just as gymnastics trains the body) [Aristotle] |
| 2807 | Some say slavery is unnatural and created by convention, and is therefore forced, and unjust [Aristotle] |
| 22582 | Spirit [thumos] is the capacity by which we love [Aristotle] |
| 2810 | Selfishness is wrong not because it is self-love, but because it is excessive [Aristotle] |
| 22555 | The function of good men is to confer benefits [Aristotle] |
| 5049 | Intelligent pleasure is the perception of beauty, order and perfection [Leibniz] |
| 22557 | Virtuous people are like the citizens of the best city [Aristotle] |
| 2841 | People become good because of nature, habit and reason [Aristotle] |
| 2829 | The law is the mean [Aristotle] |
| 22590 | Virtue is concerned with correct feelings [Aristotle] |
| 2813 | It is quite possible to live a moderate life and yet be miserable [Aristotle] |
| 22553 | Justice is a virtue of communities [Aristotle] |
| 22561 | The rich are seen as noble, because they don't need to commit crimes [Aristotle] |
| 2808 | Master and slave can have friendship through common interests [Aristotle] |
| 2803 | Man is by nature a political animal [Aristotle] |
| 2820 | People want to live together, even when they don't want mutual help [Aristotle] |
| 22586 | Only humans have reason [Aristotle] |
| 22523 | The community (of villages) becomes a city when it is totally self-sufficient [Aristotle] |
| 2805 | A community must share a common view of good and justice [Aristotle] |
| 22526 | People who are anti-social or wholly self-sufficient are no part of a city [Aristotle] |
| 22535 | Friendship is the best good for cities, because it reduces factions [Aristotle] |
| 22532 | A city can't become entirely one, because its very nature is to be a multitude [Aristotle] |
| 22584 | A community should all share to some extent in something like land or food [Aristotle] |
| 22581 | The size of a city is decided by the maximum self-sufficient community that can be surveyed [Aristotle] |
| 22548 | A city aims at living well [Aristotle] |
| 22577 | What is the best life for everyone, and is that a communal or an individual problem? [Aristotle] |
| 22579 | The same four cardinal virtues which apply to individuals also apply to a city [Aristotle] |
| 2431 | Every state is an association formed for some good purpose [Aristotle] |
| 22578 | The happiest city is the one that acts most nobly [Aristotle] |
| 2832 | The state aims to consist as far as possible of those who are like and equal [Aristotle] |
| 2821 | The six constitutions are monarchy/tyranny, aristocracy/oligarchy, and polity/democracy [Aristotle] |
| 22546 | A city is a community of free people, and the constitution should aim at the common advantage [Aristotle] |
| 2835 | Any constitution can be made to last for a day or two [Aristotle] |
| 22580 | The best constitution enables everyone to live the best life [Aristotle] |
| 22558 | Constitutions specify distribution of offices, the authorities, and the community's aim [Aristotle] |
| 22566 | The greed of the rich is more destructive than the greed of the people [Aristotle] |
| 2973 | We must decide the most desirable human life before designing a constitution [Aristotle] |
| 22563 | The middle classes are neither ambitious nor anarchic, which is good [Aristotle] |
| 2818 | The virtues of a good citizen are relative to a particular constitution [Aristotle] |
| 22545 | A person can be an excellent citizen without being an excellent man [Aristotle] |
| 22544 | A citizen is someone who is allowed to hold official posts in a city [Aristotle] |
| 22541 | Kings should be selected according to character [Aristotle] |
| 2819 | The only virtue special to a ruler is practical wisdom [Aristotle] |
| 22542 | People who buy public office will probably expect to profit from it [Aristotle] |
| 22552 | The rich can claim to rule, because of land ownership, and being more trustworthy [Aristotle] |
| 22583 | The guardians should not be harsh to strangers, as no one should behave like that [Aristotle] |
| 22543 | In large communities it is better if more people participate in the offices [Aristotle] |
| 22539 | Election of officials by the elected is dangerous, because factions can control it [Aristotle] |
| 22572 | Officers should like the constitution, be capable, and have appropriate virtues and justice [Aristotle] |
| 2826 | Like water, large numbers of people are harder to corrupt than a few [Aristotle] |
| 22567 | Democracy arises when people who are given equal freedom assume unconditional equality [Aristotle] |
| 22560 | Popular leaders only arise in democracies that are not in accord with the law [Aristotle] |
| 22562 | Choosing officials by lot is democratic [Aristotle] |
| 2823 | The many may add up to something good, even if they are inferior as individuals [Aristotle] |
| 22533 | If the people are equal in nature, then they should all share in ruling [Aristotle] |
| 2817 | It is wrong that a worthy officer of state should seek the office [Aristotle] |
| 22576 | No office is permanent in a democracy [Aristotle] |
| 22549 | In many cases, the claim that the majority is superior would apply equally to wild beasts [Aristotle] |
| 22575 | Ultimate democracy is tyranny [Aristotle] |
| 22531 | We aim to understand the best possible community for free people [Aristotle] |
| 22564 | Community is based on friends, who are equal and similar, and share things [Aristotle] |
| 22585 | Look at all of the citizens before judging a city to be happy [Aristotle] |
| 22565 | The best communities rely on a large and strong middle class [Aristotle] |
| 22589 | Citizens do not just own themselves, but are also parts of the city [Aristotle] |
| 22534 | People care less about what is communal, and more about what is their own [Aristotle] |
| 22538 | Owning and sharing property communally increases disagreements [Aristotle] |
| 22536 | There could be private land and public crops, or public land and private crops, or both public [Aristotle] |
| 22530 | Both women and children should be educated, as this contributes to a city's excellence [Aristotle] |
| 21358 | Natural slaves are those naturally belonging to another, or who can manage no more than labouring [Aristotle] |
| 20092 | One principle of liberty is to take turns ruling and being ruled [Aristotle] |
| 2833 | Equality is obviously there to help people who do not get priority in the constitution [Aristotle] |
| 2834 | It is always the weak who want justice and equality, not the strong [Aristotle] |
| 2830 | We can claim an equal right to aristocratic virtue, as well as to wealth or freedom [Aristotle] |
| 22550 | It is dreadful to neither give a share nor receive a share [Aristotle] |
| 22569 | The Heraeans replaced election with lot, to thwart campaigning [Aristotle] |
| 22568 | Faction is for inferiors to be equal, and equals to become superior [Aristotle] |
| 2814 | Phaleas proposed equality of property, provided there is equality of education [Aristotle] |
| 22540 | Wealth could be quickly leveled by only the rich giving marriage dowries [Aristotle] |
| 2828 | Law is intelligence without appetite [Aristotle] |
| 22537 | Property should be owned privately, but used communally [Aristotle] |
| 22573 | The virtue of justice may be relative to a particular constitution [Aristotle] |
| 22527 | Justice is the order in a political community [Aristotle] |
| 22547 | Justice is equality for equals, and inequality for unequals [Aristotle] |
| 2825 | The good is obviously justice, which benefits the whole community, and involves equality in some sense [Aristotle] |
| 2816 | If it is easy to change the laws, that makes them weaker [Aristotle] |
| 2806 | Man is the worst of all animals when divorced from law and justice [Aristotle] |
| 22556 | Laws that match people's habits are more effective than mere written rules [Aristotle] |
| 2827 | It is preferable that law should rule rather than any single citizen [Aristotle] |
| 22551 | Correct law should be in control, with rulers only deciding uncertain issues [Aristotle] |
| 22554 | It is said that we should not stick strictly to written law, as it is too vague [Aristotle] |
| 2840 | The whole state should pay for the worship of the gods [Aristotle] |
| 2811 | A state is plural, and needs education to make it a community [Aristotle] |
| 22588 | A city has a single end, so education must focus on that, and be communal, not private [Aristotle] |
| 2847 | The aim of serious childhood play is the amusement of the complete adult [Aristotle] |
| 2842 | Men learn partly by habit, and partly by listening [Aristotle] |
| 2844 | Abortions should be procured before the embryo has acquired life and sensation [Aristotle] |
| 2809 | If nature makes everything for a purpose, then plants and animals must have been made for man [Aristotle] |
| 2800 | The best instruments have one purpose, not many [Aristotle] |
| 2836 | God is not blessed and happy because of external goods, but because of his own nature [Aristotle] |
| 5048 | Perfection is simply quantity of reality [Leibniz] |
| 2802 | Men imagine gods to be of human shape, with a human lifestyle [Aristotle] |
| 5050 | Evil serves a greater good, and pain is necessary for higher pleasure [Leibniz] |