184 ideas
| 2136 | Philosophers become as divine and orderly as possible, by studying divinity and order [Plato] |
| 23767 | The winds of the discussion should decide its destination [Plato] |
| 23682 | It would be absurd to be precise about the small things, but only vague about the big things [Plato] |
| 2151 | Dialectic is the only method of inquiry which uproots the things which it takes for granted [Plato] |
| 2154 | The ability to take an overview is the distinguishing mark of a dialectician [Plato] |
| 4011 | For Plato, rationality is a vision of and love of a cosmic rational order [Plato, by Taylor,C] |
| 2093 | You must never go against what you actually believe [Plato] |
| 2130 | People often merely practice eristic instead of dialectic, because they don't analyse the subject-matter [Plato] |
| 2145 | In mathematics certain things have to be accepted without further explanation [Plato] |
| 10073 | There cannot be a set theory which is complete [Smith,P] |
| 10616 | Second-order arithmetic can prove new sentences of first-order [Smith,P] |
| 10075 | A 'partial function' maps only some elements to another set [Smith,P] |
| 10074 | A 'total function' maps every element to one element in another set [Smith,P] |
| 10612 | An argument is a 'fixed point' for a function if it is mapped back to itself [Smith,P] |
| 10076 | The 'range' of a function is the set of elements in the output set created by the function [Smith,P] |
| 10605 | Two functions are the same if they have the same extension [Smith,P] |
| 10615 | The Comprehension Schema says there is a property only had by things satisfying a condition [Smith,P] |
| 10595 | A 'theorem' of a theory is a sentence derived from the axioms using the proof system [Smith,P] |
| 10602 | A 'natural deduction system' has no axioms but many rules [Smith,P] |
| 10613 | No nice theory can define truth for its own language [Smith,P] |
| 10078 | An 'injective' ('one-to-one') function creates a distinct output element from each original [Smith,P] |
| 10077 | A 'surjective' ('onto') function creates every element of the output set [Smith,P] |
| 10079 | A 'bijective' function has one-to-one correspondence in both directions [Smith,P] |
| 10070 | If everything that a theory proves is true, then it is 'sound' [Smith,P] |
| 10086 | Soundness is true axioms and a truth-preserving proof system [Smith,P] |
| 10596 | A theory is 'sound' iff every theorem is true (usually from true axioms and truth-preservation) [Smith,P] |
| 10598 | A theory is 'negation complete' if it proves all sentences or their negation [Smith,P] |
| 10597 | 'Complete' applies both to whole logics, and to theories within them [Smith,P] |
| 10069 | A theory is 'negation complete' if one of its sentences or its negation can always be proved [Smith,P] |
| 10609 | Two routes to Incompleteness: semantics of sound/expressible, or syntax of consistency/proof [Smith,P] |
| 10080 | 'Effective' means simple, unintuitive, independent, controlled, dumb, and terminating [Smith,P] |
| 10087 | A theory is 'decidable' if all of its sentences could be mechanically proved [Smith,P] |
| 10088 | Any consistent, axiomatized, negation-complete formal theory is decidable [Smith,P] |
| 10081 | A set is 'enumerable' is all of its elements can result from a natural number function [Smith,P] |
| 10083 | A set is 'effectively enumerable' if a computer could eventually list every member [Smith,P] |
| 10084 | A finite set of finitely specifiable objects is always effectively enumerable (e.g. primes) [Smith,P] |
| 10085 | The set of ordered pairs of natural numbers <i,j> is effectively enumerable [Smith,P] |
| 10601 | The thorems of a nice arithmetic can be enumerated, but not the truths (so they're diffferent) [Smith,P] |
| 10600 | Being 'expressible' depends on language; being 'capture/represented' depends on axioms and proof system [Smith,P] |
| 8726 | Geometry can lead the mind upwards to truth and philosophy [Plato] |
| 10599 | For primes we write (x not= 1 ∧ ∀u∀v(u x v = x → (u = 1 ∨ v = 1))) [Smith,P] |
| 10610 | The reals contain the naturals, but the theory of reals doesn't contain the theory of naturals [Smith,P] |
| 10619 | The truths of arithmetic are just true equations and their universally quantified versions [Smith,P] |
| 10618 | All numbers are related to zero by the ancestral of the successor relation [Smith,P] |
| 10608 | The number of Fs is the 'successor' of the Gs if there is a single F that isn't G [Smith,P] |
| 10849 | Baby arithmetic covers addition and multiplication, but no general facts about numbers [Smith,P] |
| 10850 | Baby Arithmetic is complete, but not very expressive [Smith,P] |
| 10851 | Robinson Arithmetic 'Q' has basic axioms, quantifiers and first-order logic [Smith,P] |
| 10852 | Robinson Arithmetic (Q) is not negation complete [Smith,P] |
| 10068 | Natural numbers have zero, unique successors, unending, no circling back, and no strays [Smith,P] |
| 10603 | The logic of arithmetic must quantify over properties of numbers to handle induction [Smith,P] |
| 10848 | Multiplication only generates incompleteness if combined with addition and successor [Smith,P] |
| 10604 | Incompleteness results in arithmetic from combining addition and successor with multiplication [Smith,P] |
| 9863 | We aim for elevated discussion of pure numbers, not attaching them to physical objects [Plato] |
| 9864 | In pure numbers, all ones are equal, with no internal parts [Plato] |
| 8727 | Geometry is not an activity, but the study of unchanging knowledge [Plato] |
| 9861 | The same thing is both one and an unlimited number at the same time [Plato] |
| 9862 | To become rational, philosophers must rise from becoming into being [Plato] |
| 21818 | Being depends on the Good, which is not itself being, but superior to being [Plato] |
| 2061 | The best things (gods, healthy bodies, good souls) are least liable to change [Plato] |
| 6562 | Plato's reality has unchanging Parmenidean forms, and Heraclitean flux [Plato, by Fogelin] |
| 10617 | The 'ancestral' of a relation is a new relation which creates a long chain of the original relation [Smith,P] |
| 2142 | The plurality of beautiful things must belong to a single class, because they have a single particular character [Plato] |
| 5094 | Plato's Forms are said to have no location in space [Plato, by Aristotle] |
| 12043 | Forms are not universals, as they don't cover every general term [Plato, by Annas] |
| 2159 | Craftsmen making furniture refer to the form, but no one manufactures the form of furniture [Plato] |
| 17 | A Form applies to a set of particular things with the same name [Plato] |
| 12122 | Plato mistakenly thought forms were totally abstracted away from matter [Bacon on Plato] |
| 5574 | Plato's Forms not only do not come from the senses, but they are beyond possibility of sensing [Plato, by Kant] |
| 2133 | Knowledge must be of the permanent unchanging nature of things [Plato] |
| 2162 | If theory and practice conflict, the best part of the mind accepts theory, so the other part is of lower grade [Plato] |
| 2140 | True belief without knowledge is like blind people on the right road [Plato] |
| 2096 | Is the function of the mind management, authority and planning - or is it one's whole way of life? [Plato] |
| 6009 | Psychic conflict is clear if appetite is close to the body and reason fairly separate [Plato, by Modrak] |
| 6041 | There is a third element to the mind - spirit - lying between reason and appetite [Plato] |
| 2127 | The mind has parts, because we have inner conflicts [Plato] |
| 1737 | The soul seems to have an infinity of parts [Aristotle on Plato] |
| 5945 | The 'Republic' is a great work of rhetorical theory [Lawson-Tancred on Plato] |
| 23316 | For Plato and Aristotle there is no will; there is only rational desire for what is seen as good [Plato, by Frede,M] |
| 16 | We avoid evil either through a natural aversion, or because we have acquired knowledge [Plato] |
| 16565 | Without the surface decoration, poetry shows only appearances and nothing of what is real [Plato] |
| 2160 | Representation is two steps removed from the truth [Plato] |
| 2163 | Artists should be excluded from a law-abiding community, because they destroy the rational mind [Plato] |
| 2135 | Truth is closely related to proportion [Plato] |
| 2141 | I suggest that we forget about trying to define goodness itself for the time being [Plato] |
| 1869 | The good cannot be expressed in words, but imprints itself upon the soul [Plato, by Celsus] |
| 4115 | Plato found that he could only enforce rational moral justification by creating an authoritarian society [Williams,B on Plato] |
| 4547 | Plato measured the degree of reality by the degree of value [Nietzsche on Plato] |
| 2094 | A thing's function is what it alone can do, or what it does better than other things [Plato] |
| 2095 | If something has a function then it has a state of being good [Plato] |
| 2129 | Goodness is mental health, badness is mental sickness [Plato] |
| 2168 | Clever criminals do well at first, but not in the long run [Plato] |
| 12 | If we were invisible, would the just man become like the unjust? [Plato] |
| 4007 | For Plato we abandon honour and pleasure once we see the Good [Plato, by Taylor,C] |
| 2137 | The main aim is to understand goodness, which gives everything its value and advantage [Plato] |
| 2139 | Every person, and every activity, aims at the good [Plato] |
| 2143 | Good has the same role in the world of knowledge as the sun has in the physical world [Plato] |
| 2147 | The sight of goodness leads to all that is fine and true and right [Plato] |
| 2144 | Goodness makes truth and knowledge possible [Plato] |
| 2164 | Bad is always destructive, where good preserves and benefits [Plato] |
| 2138 | Pleasure is commonly thought to be the good, though the more ingenious prefer knowledge [Plato] |
| 2070 | Even people who think pleasure is the good admit that there are bad pleasures [Plato] |
| 2157 | Nice smells are intensive, have no preceding pain, and no bad after-effect [Plato] |
| 2134 | Philosophers are concerned with totally non-physical pleasures [Plato] |
| 2156 | There are three types of pleasure, for reason, for spirit and for appetite [Plato] |
| 2158 | Pleasure-seekers desperately seek illusory satisfaction, like filling a leaky vessel [Plato] |
| 2123 | Excessive pleasure deranges people, making the other virtues impossible [Plato] |
| 2166 | We should behave well even if invisible, for the health of the mind [Plato] |
| 2097 | Isn't it better to have a reputation for goodness than to actually be good? [Plato] |
| 19946 | Morality is a compromise, showing restraint, to avoid suffering wrong without compensation [Plato] |
| 5 | Justice is merely the interests of the stronger party [Plato] |
| 7 | Surely you don't return a borrowed weapon to a mad friend? [Plato] |
| 8 | Is right just the interests of the powerful? [Plato] |
| 15 | Sin first, then sacrifice to the gods from the proceeds [Plato] |
| 5944 | For Plato, virtue is its own reward [Lawson-Tancred on Plato] |
| 2155 | True goodness requires mental unity and harmony [Plato] |
| 2126 | A good community necessarily has wisdom, courage, self-discipline and morality [Plato] |
| 2092 | Simonides said morality is helping one's friends and harming one's enemies [Plato] |
| 23562 | If the parts of our soul do their correct work, we will be just people, and will act justly [Plato] |
| 19889 | People need society because the individual has too many needs [Plato] |
| 19906 | All countries are in a mutual state of nature [Locke] |
| 19882 | We are not created for solitude, but are driven into society by our needs [Locke] |
| 19864 | In nature men can dispose of possessions and their persons in any way that is possible [Locke] |
| 19865 | There is no subjection in nature, and all creatures of the same species are equal [Locke] |
| 19866 | The rational law of nature says we are all equal and independent, and should show mutual respect [Locke] |
| 19872 | The animals and fruits of the earth belong to mankind [Locke] |
| 19907 | There is a natural right to inheritance within a family [Locke] |
| 19890 | All exchanges in a community are for mutual benefit [Plato] |
| 19863 | Politics is the right to make enforceable laws to protect property and the state, for the common good [Locke] |
| 10 | After a taste of mutual harm, men make a legal contract to avoid it [Plato] |
| 5654 | The Second Treatise explores the consequences of the contractual view of the state [Locke, by Scruton] |
| 19888 | A society only begins if there is consent of all the individuals to join it [Locke] |
| 6702 | If anyone enjoys the benefits of government (even using a road) they give tacit assent to its laws [Locke] |
| 19909 | A politic society is created from a state of nature by a unanimous agreement [Locke] |
| 19910 | A single will creates the legislature, which is duty-bound to preserve that will [Locke] |
| 19893 | Anyone who enjoys the benefits of a state has given tacit consent to be part of it [Locke] |
| 19894 | You can only become an actual member of a commonwealth by an express promise [Locke] |
| 23561 | People doing their jobs properly is the fourth cardinal virtue for a city [Plato] |
| 19892 | Children are not born into citizenship of a state [Locke] |
| 19885 | Absolute monarchy is inconsistent with civil society [Locke] |
| 19886 | The idea that absolute power improves mankind is confuted by history [Locke] |
| 19903 | Despotism is arbitrary power to kill, based neither on natural equality, nor any social contract [Locke] |
| 19905 | People stripped of their property are legitimately subject to despotism [Locke] |
| 19904 | Legitimate prisoners of war are subject to despotism, because that continues the state of war [Locke] |
| 2132 | Only rule by philosophers of integrity can keep a community healthy [Plato] |
| 2149 | Reluctant rulers make a better and more unified administration [Plato] |
| 19895 | Even the legislature must be preceded by a law which gives it power to make laws [Locke] |
| 19900 | The executive must not be the legislature, or they may exempt themselves from laws [Locke] |
| 19902 | Any obstruction to the operation of the legislature can be removed forcibly by the people [Locke] |
| 19908 | Rebelling against an illegitimate power is no sin [Locke] |
| 19911 | If legislators confiscate property, or enslave people, they are no longer owed obedience [Locke] |
| 19901 | The people have supreme power, to depose a legislature which has breached their trust [Locke] |
| 19887 | Unanimous consent makes a united community, which is then ruled by the majority [Locke] |
| 2131 | Is there anything better for a community than to produce excellent people? [Plato] |
| 19913 | A master forfeits ownership of slaves he abandons [Locke] |
| 19883 | Slaves captured in a just war have no right to property, so are not part of civil society [Locke] |
| 19870 | If you try to enslave me, you have declared war on me [Locke] |
| 19871 | Freedom is not absence of laws, but living under laws arrived at by consent [Locke] |
| 19880 | All value depends on the labour involved [Locke] |
| 19884 | There is only a civil society if the members give up all of their natural executive rights [Locke] |
| 19873 | We all own our bodies, and the work we do is our own [Locke] |
| 6580 | Locke (and Marx) held that ownership of objects is a natural relation, based on the labour put into it [Locke, by Fogelin] |
| 20520 | Locke says 'mixing of labour' entitles you to land, as well as nuts and berries [Wolff,J on Locke] |
| 19875 | A man's labour gives ownership rights - as long as there are fair shares for all [Locke] |
| 19874 | If a man mixes his labour with something in Nature, he thereby comes to own it [Locke] |
| 19877 | Fountain water is everyone's, but a drawn pitcher of water has an owner [Locke] |
| 19876 | Gathering natural fruits gives ownership; the consent of other people is irrelevant [Locke] |
| 19878 | Mixing labour with a thing bestows ownership - as long as the thing is not wasted [Locke] |
| 19898 | Soldiers can be commanded to die, but not to hand over their money [Locke] |
| 19879 | A man owns land if he cultivates it, to the limits of what he needs [Locke] |
| 19881 | The aim of law is not restraint, but to make freedom possible [Locke] |
| 19868 | It is only by a law of Nature that we can justify punishing foreigners [Locke] |
| 19867 | Reparation and restraint are the only justifications for punishment [Locke] |
| 19912 | Self-defence is natural, but not the punishment of superiors by inferiors [Locke] |
| 19869 | Punishment should make crime a bad bargain, leading to repentance and deterrence [Locke] |
| 19899 | The consent of the people is essential for any tax [Locke] |
| 2152 | Dialectic is the highest and most important part of the curriculum [Plato] |
| 2148 | To gain knowledge, turn away from the world of change, and focus on true goodness [Plato] |
| 2153 | Compulsory intellectual work never remains in the mind [Plato] |
| 2630 | If Plato's God is immaterial, he will lack consciousness, wisdom, pleasure and movement, which are essential to him [Cicero on Plato] |
| 14 | If the gods are non-existent or indifferent, why bother to deceive them? [Plato] |
| 2165 | Something is unlikely to be immortal if it is imperfectly made from diverse parts [Plato] |
| 13 | Is the supreme reward for virtue to be drunk for eternity? [Plato] |
| 2120 | God is responsible for the good things, but we must look elsewhere for the cause of the bad things [Plato] |