197 ideas
13310 | Wisdom does not lie in books, and unread people can also become wise [Seneca] |
13295 | Wise people escape necessity by willing it [Seneca] |
2845 | Free and great-souled men do not keep asking "what is the use of it?" [Aristotle] |
13317 | Philosophy aims at happiness [Seneca] |
13293 | What philosophy offers humanity is guidance [Seneca] |
22521 | Our method of inquiry is to examine the smallest parts that make up the whole [Aristotle] |
13309 | That something is a necessary condition of something else doesn't mean it caused it [Seneca] |
13313 | Even philosophers have got bogged down in analysing tiny bits of language [Seneca] |
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] |
13634 | Satisfaction is 'truth in a model', which is a model of 'truth' [Shapiro] |
13643 | Aristotelian logic is complete [Shapiro] |
13651 | A set is 'transitive' if contains every member of each of its members [Shapiro] |
13647 | Choice is essential for proving downward Löwenheim-Skolem [Shapiro] |
13631 | Are sets part of logic, or part of mathematics? [Shapiro] |
13654 | It is central to the iterative conception that membership is well-founded, with no infinite descending chains [Shapiro] |
13640 | Russell's paradox shows that there are classes which are not iterative sets [Shapiro] |
13666 | Iterative sets are not Boolean; the complement of an iterative set is not an iterative sets [Shapiro] |
13653 | 'Well-ordering' of a set is an irreflexive, transitive, and binary relation with a least element [Shapiro] |
13627 | There is no 'correct' logic for natural languages [Shapiro] |
13642 | Logic is the ideal for learning new propositions on the basis of others [Shapiro] |
13668 | Bernays (1918) formulated and proved the completeness of propositional logic [Shapiro] |
13669 | Can one develop set theory first, then derive numbers, or are numbers more basic? [Shapiro] |
13667 | Skolem and Gödel championed first-order, and Zermelo, Hilbert, and Bernays championed higher-order [Shapiro] |
13662 | First-order logic was an afterthought in the development of modern logic [Shapiro] |
13624 | The 'triumph' of first-order logic may be related to logicism and the Hilbert programme, which failed [Shapiro] |
13660 | Maybe compactness, semantic effectiveness, and the Löwenheim-Skolem properties are desirable [Shapiro] |
13673 | The notion of finitude is actually built into first-order languages [Shapiro] |
15944 | Second-order logic is better than set theory, since it only adds relations and operations, and nothing else [Shapiro, by Lavine] |
13629 | Broad standard semantics, or Henkin semantics with a subclass, or many-sorted first-order semantics? [Shapiro] |
13650 | Henkin semantics has separate variables ranging over the relations and over the functions [Shapiro] |
13645 | In standard semantics for second-order logic, a single domain fixes the ranges for the variables [Shapiro] |
13649 | Completeness, Compactness and Löwenheim-Skolem fail in second-order standard semantics [Shapiro] |
13626 | Semantic consequence is ineffective in second-order logic [Shapiro] |
13637 | If a logic is incomplete, its semantic consequence relation is not effective [Shapiro] |
13632 | Finding the logical form of a sentence is difficult, and there are no criteria of correctness [Shapiro] |
13674 | We might reduce ontology by using truth of sentences and terms, instead of using objects satisfying models [Shapiro] |
13633 | 'Satisfaction' is a function from models, assignments, and formulas to {true,false} [Shapiro] |
13644 | Semantics for models uses set-theory [Shapiro] |
13636 | An axiomatization is 'categorical' if its models are isomorphic, so there is really only one interpretation [Shapiro] |
13670 | Categoricity can't be reached in a first-order language [Shapiro] |
13648 | The Löwenheim-Skolem theorems show an explosion of infinite models, so 1st-order is useless for infinity [Shapiro] |
13675 | Substitutional semantics only has countably many terms, so Upward Löwenheim-Skolem trivially fails [Shapiro] |
13658 | Downward Löwenheim-Skolem: each satisfiable countable set always has countable models [Shapiro] |
13659 | Upward Löwenheim-Skolem: each infinite model has infinite models of all sizes [Shapiro] |
13635 | 'Weakly sound' if every theorem is a logical truth; 'sound' if every deduction is a semantic consequence [Shapiro] |
13628 | We can live well without completeness in logic [Shapiro] |
13630 | Non-compactness is a strength of second-order logic, enabling characterisation of infinite structures [Shapiro] |
13646 | Compactness is derived from soundness and completeness [Shapiro] |
13661 | A language is 'semantically effective' if its logical truths are recursively enumerable [Shapiro] |
13641 | Complex numbers can be defined as reals, which are defined as rationals, then integers, then naturals [Shapiro] |
13676 | Only higher-order languages can specify that 0,1,2,... are all the natural numbers that there are [Shapiro] |
13677 | Natural numbers are the finite ordinals, and integers are equivalence classes of pairs of finite ordinals [Shapiro] |
13652 | The 'continuum' is the cardinality of the powerset of a denumerably infinite set [Shapiro] |
13657 | First-order arithmetic can't even represent basic number theory [Shapiro] |
13656 | Some sets of natural numbers are definable in set-theory but not in arithmetic [Shapiro] |
13664 | Logicism is distinctive in seeking a universal language, and denying that logic is a series of abstractions [Shapiro] |
13625 | Mathematics and logic have no border, and logic must involve mathematics and its ontology [Shapiro] |
13663 | Some reject formal properties if they are not defined, or defined impredicatively [Shapiro] |
13638 | Properties are often seen as intensional; equiangular and equilateral are different, despite identity of objects [Shapiro] |
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] |
13297 | To the four causes Plato adds a fifth, the idea which guided the event [Seneca] |
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] |
13307 | If everything can be measured, try measuring the size of a man's soul [Seneca] |
21399 | Referring to a person, and speaking about him, are very different [Seneca] |
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] |
13325 | Trouble in life comes from copying other people, which is following convention instead of reason [Seneca] |
22239 | Humans acquired the concept of virtue from an analogy with bodily health and strength [Seneca, by Allen] |
13294 | We know death, which is like before birth; ceasing to be and never beginning are the same [Seneca] |
13299 | Living is nothing wonderful; what matters is to die well [Seneca] |
13300 | It is as silly to lament ceasing to be as to lament not having lived in the remote past [Seneca] |
13321 | Is anything sweeter than valuing yourself more when you find you are loved? [Seneca] |
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] |
13292 | Selfishness does not produce happiness; to live for yourself, live for others [Seneca] |
22555 | The function of good men is to confer benefits [Aristotle] |
13303 | A man is as unhappy as he has convinced himself he is [Seneca] |
13302 | Life is like a play - it is the quality that matters, not the length [Seneca] |
13301 | We are scared of death - except when we are immersed in pleasure! [Seneca] |
13323 | The whole point of pleasure-seeking is novelty, and abandoning established ways [Seneca] |
13318 | Nature doesn't give us virtue; we must unremittingly pursue it, as a training and an art [Seneca] |
13324 | Living contrary to nature is like rowing against the stream [Seneca] |
22557 | Virtuous people are like the citizens of the best city [Aristotle] |
2841 | People become good because of nature, habit and reason [Aristotle] |
13305 | Character is ruined by not looking back over our pasts, since the future rests on the past [Seneca] |
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] |
13308 | It's no good winning lots of fights, if you are then conquered by your own temper [Seneca] |
13312 | Excessive curiosity is a form of intemperance [Seneca] |
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] |
13315 | To govern used to mean to serve, not to rule; rulers did not test their powers over those who bestowed it [Seneca] |
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] |
22569 | The Heraeans replaced election with lot, to thwart campaigning [Aristotle] |
22550 | It is dreadful to neither give a share nor receive a share [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] |
13290 | One joy of learning is making teaching possible [Seneca] |
2842 | Men learn partly by habit, and partly by listening [Aristotle] |
13322 | Both teachers and pupils should aim at one thing - the improvement of the pupil [Seneca] |
2844 | Abortions should be procured before the embryo has acquired life and sensation [Aristotle] |
13298 | Suicide may be appropriate even when it is not urgent, if there are few reasons against it [Seneca] |
13319 | If we control our own death, no one has power over us [Seneca] |
13320 | Sometimes we have a duty not to commit suicide, for those we love [Seneca] |
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] |
13311 | Does time exist on its own? Did anything precede it? Did it pre-exist the cosmos? [Seneca] |
2836 | God is not blessed and happy because of external goods, but because of his own nature [Aristotle] |
2802 | Men imagine gods to be of human shape, with a human lifestyle [Aristotle] |