52 ideas
| 5278 | Philosophy is no more than abstractions concerning observations of human historical development [Marx/Engels] |
| Full Idea: When reality is depicted, philosophy as an independent branch of knowledge loses its medium of existence. At best it is a summing up of general results, abstractions which arise from observation of the historical development of man. | |
| From: K Marx / F Engels (The German Ideology [1846], §1.A) | |
| A reaction: This strikes me as nonsense, based on a bogus Hegelian notion that history is following some sort of pattern, and that mental reality is fixed by physical conditions. The philosophy of mathematics, for one, won't fit into this definition. |
| 13520 | A 'tautology' must include connectives [Wolf,RS] |
| Full Idea: 'For every number x, x = x' is not a tautology, because it includes no connectives. | |
| From: Robert S. Wolf (A Tour through Mathematical Logic [2005], 1.2) |
| 13524 | Deduction Theorem: T∪{P}|-Q, then T|-(P→Q), which justifies Conditional Proof [Wolf,RS] |
| Full Idea: Deduction Theorem: If T ∪ {P} |- Q, then T |- (P → Q). This is the formal justification of the method of conditional proof (CPP). Its converse holds, and is essentially modus ponens. | |
| From: Robert S. Wolf (A Tour through Mathematical Logic [2005], 1.3) |
| 13522 | Universal Generalization: If we prove P(x) with no special assumptions, we can conclude ∀xP(x) [Wolf,RS] |
| Full Idea: Universal Generalization: If we can prove P(x), only assuming what sort of object x is, we may conclude ∀xP(x) for the same x. | |
| From: Robert S. Wolf (A Tour through Mathematical Logic [2005], 1.3) | |
| A reaction: This principle needs watching closely. If you pick one person in London, with no presuppositions, and it happens to be a woman, can you conclude that all the people in London are women? Fine in logic and mathematics, suspect in life. |
| 13521 | Universal Specification: ∀xP(x) implies P(t). True for all? Then true for an instance [Wolf,RS] |
| Full Idea: Universal Specification: from ∀xP(x) we may conclude P(t), where t is an appropriate term. If something is true for all members of a domain, then it is true for some particular one that we specify. | |
| From: Robert S. Wolf (A Tour through Mathematical Logic [2005], 1.3) |
| 13523 | Existential Generalization (or 'proof by example'): if we can say P(t), then we can say something is P [Wolf,RS] |
| Full Idea: Existential Generalization (or 'proof by example'): From P(t), where t is an appropriate term, we may conclude ∃xP(x). | |
| From: Robert S. Wolf (A Tour through Mathematical Logic [2005], 1.3) | |
| A reaction: It is amazing how often this vacuous-sounding principles finds itself being employed in discussions of ontology, but I don't quite understand why. |
| 13529 | Empty Set: ∃x∀y ¬(y∈x). The unique empty set exists [Wolf,RS] |
| Full Idea: Empty Set Axiom: ∃x ∀y ¬ (y ∈ x). There is a set x which has no members (no y's). The empty set exists. There is a set with no members, and by extensionality this set is unique. | |
| From: Robert S. Wolf (A Tour through Mathematical Logic [2005], 2.3) | |
| A reaction: A bit bewildering for novices. It says there is a box with nothing in it, or a pair of curly brackets with nothing between them. It seems to be the key idea in set theory, because it asserts the idea of a set over and above any possible members. |
| 13526 | Comprehension Axiom: if a collection is clearly specified, it is a set [Wolf,RS] |
| Full Idea: The comprehension axiom says that any collection of objects that can be clearly specified can be considered to be a set. | |
| From: Robert S. Wolf (A Tour through Mathematical Logic [2005], 2.2) | |
| A reaction: This is virtually tautological, since I presume that 'clearly specified' means pinning down exact which items are the members, which is what a set is (by extensionality). The naïve version is, of course, not so hot. |
| 13534 | In first-order logic syntactic and semantic consequence (|- and |=) nicely coincide [Wolf,RS] |
| Full Idea: One of the most appealing features of first-order logic is that the two 'turnstiles' (the syntactic single |-, and the semantic double |=), which are the two reasonable notions of logical consequence, actually coincide. | |
| From: Robert S. Wolf (A Tour through Mathematical Logic [2005], 5.3) | |
| A reaction: In the excitement about the possibility of second-order logic, plural quantification etc., it seems easy to forget the virtues of the basic system that is the target of the rebellion. The issue is how much can be 'expressed' in first-order logic. |
| 13535 | First-order logic is weakly complete (valid sentences are provable); we can't prove every sentence or its negation [Wolf,RS] |
| Full Idea: The 'completeness' of first order-logic does not mean that every sentence or its negation is provable in first-order logic. We have instead the weaker result that every valid sentence is provable. | |
| From: Robert S. Wolf (A Tour through Mathematical Logic [2005], 5.3) | |
| A reaction: Peter Smith calls the stronger version 'negation completeness'. |
| 13531 | Model theory reveals the structures of mathematics [Wolf,RS] |
| Full Idea: Model theory helps one to understand what it takes to specify a mathematical structure uniquely. | |
| From: Robert S. Wolf (A Tour through Mathematical Logic [2005], 5.1) | |
| A reaction: Thus it is the development of model theory which has led to the 'structuralist' view of mathematics. |
| 13532 | Model theory 'structures' have a 'universe', some 'relations', some 'functions', and some 'constants' [Wolf,RS] |
| Full Idea: A 'structure' in model theory has a non-empty set, the 'universe', as domain of variables, a subset for each 'relation', some 'functions', and 'constants'. | |
| From: Robert S. Wolf (A Tour through Mathematical Logic [2005], 5.2) |
| 13519 | Model theory uses sets to show that mathematical deduction fits mathematical truth [Wolf,RS] |
| Full Idea: Model theory uses set theory to show that the theorem-proving power of the usual methods of deduction in mathematics corresponds perfectly to what must be true in actual mathematical structures. | |
| From: Robert S. Wolf (A Tour through Mathematical Logic [2005], Pref) | |
| A reaction: That more or less says that model theory demonstrates the 'soundness' of mathematics (though normal arithmetic is famously not 'complete'). Of course, he says they 'correspond' to the truths, rather than entailing them. |
| 13533 | First-order model theory rests on completeness, compactness, and the Löwenheim-Skolem-Tarski theorem [Wolf,RS] |
| Full Idea: The three foundations of first-order model theory are the Completeness theorem, the Compactness theorem, and the Löwenheim-Skolem-Tarski theorem. | |
| From: Robert S. Wolf (A Tour through Mathematical Logic [2005], 5.3) | |
| A reaction: On p.180 he notes that Compactness and LST make no mention of |- and are purely semantic, where Completeness shows the equivalence of |- and |=. All three fail for second-order logic (p.223). |
| 13537 | An 'isomorphism' is a bijection that preserves all structural components [Wolf,RS] |
| Full Idea: An 'isomorphism' is a bijection between two sets that preserves all structural components. The interpretations of each constant symbol are mapped across, and functions map the relation and function symbols. | |
| From: Robert S. Wolf (A Tour through Mathematical Logic [2005], 5.4) |
| 13539 | The LST Theorem is a serious limitation of first-order logic [Wolf,RS] |
| Full Idea: The Löwenheim-Skolem-Tarski theorem demonstrates a serious limitation of first-order logic, and is one of primary reasons for considering stronger logics. | |
| From: Robert S. Wolf (A Tour through Mathematical Logic [2005], 5.7) |
| 13538 | If a theory is complete, only a more powerful language can strengthen it [Wolf,RS] |
| Full Idea: It is valuable to know that a theory is complete, because then we know it cannot be strengthened without passing to a more powerful language. | |
| From: Robert S. Wolf (A Tour through Mathematical Logic [2005], 5.5) |
| 13525 | Most deductive logic (unlike ordinary reasoning) is 'monotonic' - we don't retract after new givens [Wolf,RS] |
| Full Idea: Deductive logic, including first-order logic and other types of logic used in mathematics, is 'monotonic'. This means that we never retract a theorem on the basis of new givens. If T|-φ and T⊆SW, then S|-φ. Ordinary reasoning is nonmonotonic. | |
| From: Robert S. Wolf (A Tour through Mathematical Logic [2005], 1.7) | |
| A reaction: The classic example of nonmonotonic reasoning is the induction that 'all birds can fly', which is retracted when the bird turns out to be a penguin. He says nonmonotonic logic is a rich field in computer science. |
| 13530 | An ordinal is an equivalence class of well-orderings, or a transitive set whose members are transitive [Wolf,RS] |
| Full Idea: Less theoretically, an ordinal is an equivalence class of well-orderings. Formally, we say a set is 'transitive' if every member of it is a subset of it, and an ordinal is a transitive set, all of whose members are transitive. | |
| From: Robert S. Wolf (A Tour through Mathematical Logic [2005], 2.4) | |
| A reaction: He glosses 'transitive' as 'every member of a member of it is a member of it'. So it's membership all the way down. This is the von Neumann rather than the Zermelo approach (which is based on singletons). |
| 13518 | Modern mathematics has unified all of its objects within set theory [Wolf,RS] |
| Full Idea: One of the great achievements of modern mathematics has been the unification of its many types of objects. It began with showing geometric objects numerically or algebraically, and culminated with set theory representing all the normal objects. | |
| From: Robert S. Wolf (A Tour through Mathematical Logic [2005], Pref) | |
| A reaction: His use of the word 'object' begs all sorts of questions, if you are arriving from the street, where an object is something which can cause a bruise - but get used to it, because the word 'object' has been borrowed for new uses. |
| 5287 | Philosophical problems are resolved into empirical facts [Marx/Engels] |
| Full Idea: Every profound philosophical problem is resolved quite simply into an empirical fact. | |
| From: K Marx / F Engels (The German Ideology [1846], §1.B) | |
| A reaction: This shows that empirical accounts of metaphysics are not just a branch of British empiricism, but are a basic fact of any materialist view of the world. The influence of David Hume, however, hovers behind this Marxist doctrine. |
| 5303 | For the proletariate, law, morality and religion are just expressions of bourgeois interests [Marx/Engels] |
| Full Idea: Law, morality, religion are to the proletarian so many bourgeois prejudices, behind which lurk in ambush just as many bourgeois interests. | |
| From: K Marx / F Engels (The Communist Manifesto [1848], §1) | |
| A reaction: This Marxist idea has been the main driving force in spreading relativist views through modern culture. There is a lot of truth here, but philosophy is plausibly the search for truths which both the bourgeois and the proletarian will accept. |
| 23872 | 'Society determines consciousness' is contradictory; society only exists in minds [Weil on Marx/Engels] |
| Full Idea: In the Marxist formula 'social existence determines consciousness' there are more contradictions than words. Since 'social' can only exist in human minds, 'social existence' is already consciousness. It cannot determine consciousness, which is undefined. | |
| From: comment on K Marx / F Engels (The German Ideology [1846]) by Simone Weil - Fragments p.126 | |
| A reaction: I'm not convinced that society only exists in minds. Many children in Victorian London had never heard of 'London', but that didn't stop it existing. Our problems are often social substrata of which we are unaware. |
| 5277 | Life is not determined by consciousness, but consciousness by life [Marx/Engels] |
| Full Idea: Life is not determined by consciousness, but consciousness by life. | |
| From: K Marx / F Engels (The German Ideology [1846], §1.A) | |
| A reaction: This slogan is the heart of Marxism. It begs the obvious question of what determines (social) life? Aristotle is at least partly right - that some activities and social organisation are 'unnatural', going against the grain of the human 'given'. |
| 5280 | Language co-exists with consciousness, and makes it social [Marx/Engels] |
| Full Idea: Language is as old as consciousness, language is practical consciousness that exists also for other men. | |
| From: K Marx / F Engels (The German Ideology [1846], §1.A) | |
| A reaction: Dennett takes a similar view - that consciousness is more-or-less a consequence of the development of consciousness. This is understandable if you make intentional rather than phenomenal consciousness central. Otherwise ants may well have it. |
| 5276 | The nature of an individual coincides with what they produce and how they produce it [Marx/Engels] |
| Full Idea: As individuals express their life, so they are; what they are, therefore, coincides with their production, both with what they produce and with how they produce. | |
| From: K Marx / F Engels (The German Ideology [1846], §1.A) | |
| A reaction: This appears to be contradicted by their subsequent idea that 'alienation' from the means of production is possible. Presumably intellectuals (in all ages) are to some extent exempt from this rule. It is, in fact, not true. |
| 5281 | Consciousness is a social product [Marx/Engels] |
| Full Idea: Consciousness is from the very beginning a social product. | |
| From: K Marx / F Engels (The German Ideology [1846], §1.A) | |
| A reaction: This slogan has produced the sociological view of truth which has stood opposed to philosophy for the last 150 years. It would be silly to deny that there is a good point here, but equally silly to think that all consciousness is explicable in this way. |
| 21998 | Bourgeois interests create our morality, law and religion [Marx/Engels] |
| Full Idea: Morality, law and religion are bourgeois prejudices, behind which lurk in ambush just as many bourgeois interests. | |
| From: K Marx / F Engels (The Communist Manifesto [1848], p.230), quoted by Peter Singer - Marx 9 | |
| A reaction: The obvious question is whether this creation of values is conscious or unconscious. Personally I believe in conspiracies. Some cynical conversations go on behind the scenes, of which historians will never hear. |
| 5289 | When aristocracy or the bourgeoisie dominate, certain values dominate with them [Marx/Engels] |
| Full Idea: During the time that the aristocracy was dominant, the concepts honour, loyalty etc. were dominant, and during the dominance of the bourgeoisie the concepts of freedom, equality etc. | |
| From: K Marx / F Engels (The German Ideology [1846], §1.B) | |
| A reaction: This is a very anti-Aristotelian view, based on a very different idea of human nature. It must, to some extent, be true, but freedom and equality will be a value for the proletariat, and loyalty will be a key value if the family is central. |
| 5274 | Young Hegelians proposed changing our present consciousness for liberating critical consciousness [Marx/Engels] |
| Full Idea: The Young Hegelians logically put to men the moral postulate of exchanging their present consciousness for human, critical or egoistic consciousness, and thus removing their limitations. | |
| From: K Marx / F Engels (The German Ideology [1846], §1.A) | |
| A reaction: It seems there are three views here: this one (that we can change our consciousness), the Aristotelian view (that consciousness is 'given'), and the Marxist view (that society determines consciousness). The truth is somewhere between them. |
| 21992 | Producing their own subsistence distinguishes men from animals [Marx/Engels] |
| Full Idea: Men begin to distinguish themselves from animals as soon as they begin to produce their means of subsistence. | |
| From: K Marx / F Engels (The German Ideology [1846], p.160), quoted by Sydney Shoemaker - Some varieties of functionalism 6 | |
| A reaction: At the very least, we must say that there had to be some intrinsic distinctiveness in place before men could do this. I like meta-thought. |
| 5275 | Men distinguish themselves from animals when they begin to produce their means of subsistence [Marx/Engels] |
| Full Idea: Men begin to distinguish themselves from animals as soon as they begin to produce their means of subsistence. | |
| From: K Marx / F Engels (The German Ideology [1846], §1.A) | |
| A reaction: This seems a rather external criterion. Presumably we can ask what biological or mental feature made it possible for men to produce their own means of subsistence, and why it evolved. Darwin puts a different perspective on this idea. |
| 5292 | Individuals are mutually hostile unless they group together in competition with other groups [Marx/Engels] |
| Full Idea: Separate individuals form a class only insofar as they have to carry on a battle against another class; otherwise they are on hostile terms with each other as competitors. | |
| From: K Marx / F Engels (The German Ideology [1846], §1.D) | |
| A reaction: Beneath the Marxist view that consciousness is a social creation lies a Hobbesian pessimism about basic human nature. This idea bodes ill for ultimate communism, because class struggle will have been abolished. What, then, can unite people? |
| 5293 | Only in community are people able to cultivate their gifts, and therefore be free [Marx/Engels] |
| Full Idea: Only in community with others has each individual the means of cultivating his gifts in all directions; only in the community, therefore, is personal freedom possible. | |
| From: K Marx / F Engels (The German Ideology [1846], §1.D) | |
| A reaction: This is where Aristotle and Marx agree, and I agree too. I think we could drop the word "free", which is to some degree a necessary right and precondition of human happiness, but is not the real target. |
| 5273 | Young Hegelians think consciousness is chains for men, where old Hegelians think it the bond of society [Marx/Engels] |
| Full Idea: The Young Hegelians consider conceptions, thoughts, ideas, in fact all the products of consciousness, to which they attribute an independent existence, as the real chains of men (just as the Old Hegelians declared them the true bonds of human society). | |
| From: K Marx / F Engels (The German Ideology [1846], §1.A) | |
| A reaction: Marx and Engels will attack both views. The Young Hegelians seem potential existentialists, and the Old Hegelians followers of Aristotle. The correct view is somewhere in the middle. Self-criticism is an option given to us by our culture. |
| 5283 | In communist society we are not trapped in one activity, but can act freely [Marx/Engels] |
| Full Idea: In communist society, where nobody has one exclusive sphere of activity but each can become accomplished in any branch he wishes, society regulates production, and I can hunt in the morning, fish in the afternoon and criticise after dinner. | |
| From: K Marx / F Engels (The German Ideology [1846], §1.A) | |
| A reaction: This sounds like a hopeless daydream, and Plato would be appalled. It now (2004) looks as if this aspiration is more likely to be met in a liberal capitalist democracy than it is under any state-controlled communism. |
| 5282 | If the common interest imposes on the individual, his actions become alienated and enslaving [Marx/Engels] |
| Full Idea: As long as a cleavage exists between the particular and the common interest, as long, therefore, as activity is not voluntarily, but naturally divided, man's own deed becomes an alien power opposed to him, which enslaves him. | |
| From: K Marx / F Engels (The German Ideology [1846], §1.A) | |
| A reaction: An isolated individual could feel 'alienated' doing menial tasks for themselves when they yearned to get on with their poetry. Alienation is not all-or-nothing. Compare working for a good employer with working for Nazi conquerors. |
| 5288 | The class controlling material production also controls mental production [Marx/Engels] |
| Full Idea: The class which has the means of material production at its disposal, has control at the same time over the means of mental production. | |
| From: K Marx / F Engels (The German Ideology [1846], §1.B) | |
| A reaction: This is mostly true, because the wealthy will control both the media and most of the educational institutions, but in a world of universal education and underground presses it doesn't seem to be a necessary truth. Wide dissemination of ideas needs money. |
| 5290 | The revolutionary class is opposed to 'class', and represents all of society [Marx/Engels] |
| Full Idea: The class making a revolution appears from the very start, if only because it is opposed to a 'class', not as a class but as the representative of the whole of society. | |
| From: K Marx / F Engels (The German Ideology [1846], §1.B) | |
| A reaction: This appears to be the source of most of the troubles of the last 150 years. Aristotle thought a benevolent tyrant could represent all of society. It looks to me as if a representative democracy has the best chance, but control of the media is tricky. |
| 5294 | To assert themselves as individuals, the proletarians must overthrow the State [Marx/Engels] |
| Full Idea: In order to assert themselves as individuals, the proletarians must overthrow the State. | |
| From: K Marx / F Engels (The German Ideology [1846], §1.D) | |
| A reaction: By the 'State' is here meant the centralised power of the owners of the means of production. They are not aiming at anarchism, but at a more fluid 'society' or 'community'. Most of us have an Orwellian fear of violent 'overthrowing'. |
| 5302 | Modern governments are just bourgeois management committees [Marx/Engels] |
| Full Idea: The executive of the modern State is but a committee for managing the common affairs of the whole bourgeoisie. | |
| From: K Marx / F Engels (The Communist Manifesto [1848], §1) | |
| A reaction: In Britain the Labour Party and the Trade Unions have appeared since 1848, but bourgeoisie control of the media has pushed us a long way back towards Marx's time. Government will always be someone's management committee. |
| 5304 | Communism aims to abolish not all property, but bourgeois property [Marx/Engels] |
| Full Idea: The distinguishing feature of Communism is not the abolition of property generally, but the abolition of bourgeois property. | |
| From: K Marx / F Engels (The Communist Manifesto [1848], §2) | |
| A reaction: This is a sinister remark which has led to huge numbers of murders in the Soviet Union and China. People resent having their property 'abolished', especially if they have worked hard for it. But most of our wealth is owned by about 2% of our people. |
| 5307 | Many of the bourgeois rights grievances are a form of self-defence [Marx/Engels] |
| Full Idea: A part of the bourgeoisie is desirous of redressing social grievances, in order to secure the continued existence of bourgeois society. | |
| From: K Marx / F Engels (The Communist Manifesto [1848], §3.II) | |
| A reaction: …so don't try being nice to us. No TRUE bourgeois would actually want to help the proletariate… Nevertheless, he is probably largely right. Do we want the poor to suffer? No. Do we want them to be as rich as us? No! |
| 5285 | Slavery cannot be abolished without the steam-engine [Marx/Engels] |
| Full Idea: Slavery cannot be abolished without the steam-engine. | |
| From: K Marx / F Engels (The German Ideology [1846], §1.B) | |
| A reaction: In Britain and its colonies it does appear that the rise of factories and the abolition of slavery coincided. It is hard to see why this should be a necessity, though. Did the early Christians keep slaves? Some ancient Greeks objected to slavery. |
| 5284 | Communism abolishes private property and dissolves the powerful world market [Marx/Engels] |
| Full Idea: It is empirically established that by the overthrow of the existing state of society by the communist revolution, and the abolition of private property, which is identical with it, the power of the world market will be dissolved. | |
| From: K Marx / F Engels (The German Ideology [1846], §1.A) | |
| A reaction: They later dropped the abolition of private property as an aim. They were very early in spotting the problem of global capitalism. As long as there are scarcities of anything (e.g. Rembrandts) it is hard to imagine the disappearance of the market. |
| 5306 | The free development of each should be the condition for the free development of all [Marx/Engels] |
| Full Idea: In a communist society we shall have an association, in which the free development of each is the condition for the free development of all. | |
| From: K Marx / F Engels (The Communist Manifesto [1848], §2) | |
| A reaction: This ringing slogan is remarkably close to John Stuart Mill's defence of liberalism, where liberty is an absolute, as long as it avoids the liberty of others. Personally I think freedom is marginal in political philosophy, like food and shelter. |
| 5291 | The law says private property is the result of the general will [Marx/Engels] |
| Full Idea: In civil law the existing property relations are declared to be the result of the general will. | |
| From: K Marx / F Engels (The German Ideology [1846], §1.C) | |
| A reaction: In other words, the 'general will' is open to endless abuse, because it is defined by the current power group, which nowadays is whoever controls the mass media. Even a 'free' election doesn't prove the general will, which is a cultural thing. |
| 5305 | Communists want to rescue education from the ruling class [Marx/Engels] |
| Full Idea: Communists seek to rescue education from the influence of the ruling class. | |
| From: K Marx / F Engels (The Communist Manifesto [1848], §2) | |
| A reaction: Someone has to control education, and I would personally prefer it if the controllers were well educated themselves. Neutral education is an idle dream. We must educate for democracy, if we really want democracy. |
| 5279 | Human history must always be studied in relation to industry and exchange [Marx/Engels] |
| Full Idea: The 'history of humanity' must always be studied and treated in relation to the history of industry and exchange. | |
| From: K Marx / F Engels (The German Ideology [1846], §1.A) | |
| A reaction: There is a lot of truth in this, but why did the Greeks produce Pythagoras, or the Jews produce Jesus, or the British produce Sid Vicious? Two very similar industrial societies can produce very different cultures. Individuals can make a difference. |
| 5286 | Most historians are trapped in the illusions of their own epoch [Marx/Engels] |
| Full Idea: Most historians see in history just the political actions of princes and states, religious and all sorts of theoretical struggles, and in particular in each historical epoch have had to share the illusion of that epoch. | |
| From: K Marx / F Engels (The German Ideology [1846], §1.B) | |
| A reaction: Is it an illusion of our epoch that we share the illusions of our epoch? It seems unfair to say that Marx and Engels can see beyond the illusions of their epoch, but some historian writing about the Wars of the Roses can't. Princes were important. |
| 5301 | The history of all existing society is the history of class struggles [Marx/Engels] |
| Full Idea: The history of all existing society is the history of class struggles. | |
| From: K Marx / F Engels (The Communist Manifesto [1848], §1) | |
| A reaction: This seems to make, say, the English Peasants' Revolt of 1481 crucial, and the building of Lincoln Cathedral fairly minor. Where does the advent of the telephone figure? Etc. Still, we must concede his point. Most medieval history is about power. |
| 3029 | Stilpo said if Athena is a daughter of Zeus, then a statue is only the child of a sculptor, and so is not a god [Stilpo, by Diog. Laertius] |
| Full Idea: Stilpo asked a man whether Athena is the daughter of Zeus, and when he said yes, said,"But this statue of Athena by Phidias is the child of Phidias, so it is not a god." | |
| From: report of Stilpo (fragments/reports [c.330 BCE]) by Diogenes Laertius - Lives of Eminent Philosophers 02.10.5 |