110 ideas
| 1597 | Thales was the first western thinker to believe the arché was intelligible [Roochnik on Thales] |
| 10987 | Three traditional names of rules are 'Simplification', 'Addition' and 'Disjunctive Syllogism' [Read] |
| 11004 | Necessity is provability in S4, and true in all worlds in S5 [Read] |
| 11018 | There are fuzzy predicates (and sets), and fuzzy quantifiers and modifiers [Read] |
| 11011 | Same say there are positive, negative and neuter free logics [Read] |
| 11020 | Realisms like the full Comprehension Principle, that all good concepts determine sets [Read] |
| 14187 | If logic is topic-neutral that means it delves into all subjects, rather than having a pure subject matter [Read] |
| 10986 | Not all validity is captured in first-order logic [Read] |
| 10972 | The non-emptiness of the domain is characteristic of classical logic [Read] |
| 11024 | Semantics must precede proof in higher-order logics, since they are incomplete [Read] |
| 10985 | We should exclude second-order logic, precisely because it captures arithmetic [Read] |
| 14188 | Not all arguments are valid because of form; validity is just true premises and false conclusion being impossible [Read] |
| 14182 | If the logic of 'taller of' rests just on meaning, then logic may be the study of merely formal consequence [Read] |
| 14183 | Maybe arguments are only valid when suppressed premises are all stated - but why? [Read] |
| 10970 | A theory of logical consequence is a conceptual analysis, and a set of validity techniques [Read] |
| 10984 | Logical consequence isn't just a matter of form; it depends on connections like round-square [Read] |
| 14184 | In modus ponens the 'if-then' premise contributes nothing if the conclusion follows anyway [Read] |
| 14186 | Logical connectives contain no information, but just record combination relations between facts [Read] |
| 10973 | A theory is logically closed, which means infinite premisses [Read] |
| 11007 | Quantifiers are second-order predicates [Read] |
| 10978 | In second-order logic the higher-order variables range over all the properties of the objects [Read] |
| 10971 | A logical truth is the conclusion of a valid inference with no premisses [Read] |
| 10988 | Any first-order theory of sets is inadequate [Read] |
| 10974 | Compactness is when any consequence of infinite propositions is the consequence of a finite subset [Read] |
| 10975 | Compactness does not deny that an inference can have infinitely many premisses [Read] |
| 10977 | Compactness blocks the proof of 'for every n, A(n)' (as the proof would be infinite) [Read] |
| 10976 | Compactness makes consequence manageable, but restricts expressive power [Read] |
| 11014 | Self-reference paradoxes seem to arise only when falsity is involved [Read] |
| 11025 | Infinite cuts and successors seems to suggest an actual infinity there waiting for us [Read] |
| 10979 | Although second-order arithmetic is incomplete, it can fully model normal arithmetic [Read] |
| 10980 | Second-order arithmetic covers all properties, ensuring categoricity [Read] |
| 10997 | Von Neumann numbers are helpful, but don't correctly describe numbers [Read] |
| 11016 | Would a language without vagueness be usable at all? [Read] |
| 11019 | Supervaluations say there is a cut-off somewhere, but at no particular place [Read] |
| 11012 | A 'supervaluation' gives a proposition consistent truth-value for classical assignments [Read] |
| 11013 | Identities and the Indiscernibility of Identicals don't work with supervaluations [Read] |
| 10995 | A haecceity is a set of individual properties, essential to each thing [Read] |
| 11001 | Equating necessity with truth in every possible world is the S5 conception of necessity [Read] |
| 10992 | The point of conditionals is to show that one will accept modus ponens [Read] |
| 10989 | The standard view of conditionals is that they are truth-functional [Read] |
| 11017 | Some people even claim that conditionals do not express propositions [Read] |
| 14185 | Conditionals are just a shorthand for some proof, leaving out the details [Read] |
| 3013 | Nothing is stronger than necessity, which rules everything [Thales, by Diog. Laertius] |
| 10983 | Knowledge of possible worlds is not causal, but is an ontology entailed by semantics [Read] |
| 10982 | How can modal Platonists know the truth of a modal proposition? [Read] |
| 10996 | Actualism is reductionist (to parts of actuality), or moderate realist (accepting real abstractions) [Read] |
| 10981 | A possible world is a determination of the truth-values of all propositions of a domain [Read] |
| 11000 | If worlds are concrete, objects can't be present in more than one, and can only have counterparts [Read] |
| 10998 | The mind abstracts ways things might be, which are nonetheless real [Read] |
| 11005 | Negative existentials with compositionality make the whole sentence meaningless [Read] |
| 10966 | A proposition objectifies what a sentence says, as indicative, with secure references [Read] |
| 19956 | True goodness is political, and consists of love of and submission to the laws [Montesquieu] |
| 19961 | Primitive people would be too vulnerable and timid to attack anyone, so peace would reign [Montesquieu] |
| 19962 | Men do not desire to subjugate one another; domination is a complex and advanced idea [Montesquieu] |
| 19963 | People are drawn into society by needs, shared fears, pleasure, and knowledge [Montesquieu] |
| 20008 | People are guided by a multitude of influences, from which the spirit of a nation emerges [Montesquieu] |
| 19993 | In small republics citizens identify with the public good, and abuses are fewer [Montesquieu] |
| 19992 | In a large republic there is too much wealth for individuals to manage it [Montesquieu] |
| 20005 | The rich would never submit to a lottery deciding which part of their society should be slaves [Montesquieu] |
| 19995 | All states aim at preservation, and then have distinctive individual purposes [Montesquieu] |
| 19964 | The natural power of a father suggests rule by one person, but that authority can be spread [Montesquieu] |
| 19986 | Monarchies can act more quickly, because one person is in charge [Montesquieu] |
| 19972 | The nobility are an indispensable part of a monarchy [Montesquieu] |
| 19974 | Monarchs must not just have links to the people; they need a body which maintains the laws [Montesquieu] |
| 19976 | Ambition is good in a monarchy, because the monarch can always restrain it [Montesquieu] |
| 19978 | In monarchies, men's actions are judged by their grand appearance, not their virtues [Montesquieu] |
| 19985 | In a monarchy, the nobility must be hereditary, to bind them together [Montesquieu] |
| 19988 | A despot's agents must be given power, so they inevitably become corrupt [Montesquieu] |
| 19977 | Despotism and honour are incompatible, because honour scorns his power, and lives by rules [Montesquieu] |
| 20007 | Tyranny is either real violence, or the imposition of unpopular legislation [Montesquieu] |
| 19975 | Despots are always lazy and ignorant, so they always delegate their power to a vizier [Montesquieu] |
| 19989 | The will of a despot is an enigma, so magistrates can only follow their own will [Montesquieu] |
| 19970 | If the nobility is numerous, the senate is the artistocracy, and the nobles are a democracy [Montesquieu] |
| 19971 | Aristocracy is democratic if they resemble the people, but not if they resemble the monarch [Montesquieu] |
| 19984 | Great inequality between aristocrats and the rest is bad - and also among aristocrats themselves [Montesquieu] |
| 19980 | If a government is to be preserved, it must first be loved [Montesquieu] |
| 19996 | A government has a legislature, an international executive, and a domestic executive [Montesquieu] |
| 19997 | The judiciary must be separate from the legislature, to avoid arbitrary power [Montesquieu] |
| 19965 | The fundamental laws of a democracy decide who can vote [Montesquieu] |
| 19968 | It is basic to a democracy that the people themselves must name their ministers [Montesquieu] |
| 19969 | Voting should be public, so the lower classes can be influenced by the example of notable people [Montesquieu] |
| 19999 | All citizens (apart from the very humble poor) should choose their representatives [Montesquieu] |
| 19967 | In a democracy the people should manage themselves, and only delegate what they can't do [Montesquieu] |
| 19966 | A democratic assembly must have a fixed number, to see whether everyone has spoken [Montesquieu] |
| 19998 | If deputies represent people, they are accountable, but less so if they represent places [Montesquieu] |
| 20003 | Slaves are not members of the society, so no law can forbid them to run away [Montesquieu] |
| 20000 | Slavery is entirely bad; the master abandons the virtues, and they are pointless in the slave [Montesquieu] |
| 20006 | The demand for slavery is just the masters' demand for luxury [Montesquieu] |
| 20009 | Freedom of speech and writing, within the law, is essential to preserve liberty [Montesquieu] |
| 19994 | Freedom in society is ability to do what is right, and not having to do what is wrong [Montesquieu] |
| 19981 | No one even thinks of equality in monarchies and despotism; they all want superiority [Montesquieu] |
| 19991 | Equality is not command by everyone or no one, but command and obedience among equals [Montesquieu] |
| 19990 | Democracy is corrupted by lack of equality, or by extreme equality (between rulers and ruled) [Montesquieu] |
| 19983 | Democracies may sometimes need to restrict equality [Montesquieu] |
| 19982 | Some equality can be achieved by social categories, combined with taxes and poor relief [Montesquieu] |
| 19959 | Prior to positive laws there is natural equity, of obedience, gratitude, dependence and merit [Montesquieu] |
| 19960 | Sensation gives animals natural laws, but knowledge can make them break them [Montesquieu] |
| 20002 | The death penalty is permissible, because its victims enjoyed the protection of that law [Montesquieu] |
| 20010 | If religion teaches determinism, penalties must be severe; if free will, then that is different [Montesquieu] |
| 20001 | The only right victors have over captives is the protection of the former [Montesquieu] |
| 19973 | The clergy are essential to a monarchy, but dangerous in a republic [Montesquieu] |
| 19987 | Religion has the most influence in despotic states, and reinforces veneration for the ruler [Montesquieu] |
| 20011 | Religion can support the state when the law fails to do so [Montesquieu] |
| 20004 | French slavery was accepted because it was the best method of religious conversion [Montesquieu] |
| 19979 | In monarchies education ennobles people, and in despotisms it debases them [Montesquieu] |
| 19957 | Teaching is the best practice of the general virtue that leads us to love everyone [Montesquieu] |
| 1494 | Thales said water is the first principle, perhaps from observing that food is moist [Thales, by Aristotle] |
| 19958 | Laws are the necessary relations that derive from the nature of things [Montesquieu] |
| 1713 | Thales must have thought soul causes movement, since he thought magnets have soul [Thales, by Aristotle] |
| 1742 | Thales said the gods know our wrong thoughts as well as our evil actions [Thales, by Diog. Laertius] |