59 ideas
| 18450 | Philosophy has its own mode of death, by separating soul from body [Porphyry] |
| Full Idea: There is a double death. One, known by all men, consists in the separation of the body with the soul; the other, characteristic of philosophers, results in the separation of the soul from the body. | |
| From: Porphyry (Launching Points to the Realm of the Mind [c.280], 1Enn9 3) |
| 2056 | Philosophers are always switching direction to something more interesting [Plato] |
| Full Idea: Philosophers are always ready to change direction, if a topic crops up which is more attractive than the one to hand. | |
| From: Plato (Theaetetus [c.368 BCE], 172d) | |
| A reaction: Which sounds trivial, but it may be what God does. |
| 2086 | Understanding mainly involves knowing the elements, not their combinations [Plato] |
| Full Idea: A perfect grasp of any subject depends far more on knowing elements than on knowing complexes. | |
| From: Plato (Theaetetus [c.368 BCE], 206b) |
| 2083 | Either a syllable is its letters (making parts as knowable as whole) or it isn't (meaning it has no parts) [Plato] |
| Full Idea: Either a syllable is not the same as its letters, in which case it cannot have the letters as parts of itself, or it is the same as its letters, in which case these basic elements are just as knowable as it is. | |
| From: Plato (Theaetetus [c.368 BCE], 205b) |
| 2082 | A rational account is essentially a weaving together of things with names [Plato] |
| Full Idea: Just as primary elements are woven together, so their names may be woven together to produce a spoken account, because an account is essentially a weaving together of names. | |
| From: Plato (Theaetetus [c.368 BCE], 202b) | |
| A reaction: If justification requires 'logos', and logos is a 'weaving together of names', then Plato might be taken as endorsing the coherence account of justification. Or do the two 'weavings' correspond? |
| 2052 | Eristic discussion is aggressive, but dialectic aims to help one's companions in discussion [Plato] |
| Full Idea: Eristic discussions involve as many tricks and traps as possible, but dialectical discussions involve being serious and correcting the interlocutor's mistakes only when they are his own fault or the result of past conditioning. | |
| From: Plato (Theaetetus [c.368 BCE], 167e) |
| 15854 | A primary element has only a name, and no logos, but complexes have an account, by weaving the names [Plato] |
| Full Idea: A primary element cannot be expressed in an account; it can only be named, for a name is all that it has. But with the things composed of these ...just as the elements are woven together, so the names can woven to become an account. | |
| From: Plato (Theaetetus [c.368 BCE], 202b01-3) | |
| A reaction: This is the beginning of what I see as Aristotle's metaphysics, as derived from his epistemology, that is, ontology is what explains, and what we can give an account [logos] of. Aristotle treats this under 'definitions'. |
| 13949 | All models of Peano axioms are isomorphic, so the models all seem equally good for natural numbers [Cartwright,R on Peano] |
| Full Idea: Peano's axioms are categorical (any two models are isomorphic). Some conclude that the concept of natural number is adequately represented by them, but we cannot identify natural numbers with one rather than another of the isomorphic models. | |
| From: comment on Giuseppe Peano (Principles of Arithmetic, by a new method [1889], 11) by Richard Cartwright - Propositions 11 | |
| A reaction: This is a striking anticipation of Benacerraf's famous point about different set theory accounts of numbers, where all models seem to work equally well. Cartwright is saying that others have pointed this out. |
| 18113 | PA concerns any entities which satisfy the axioms [Peano, by Bostock] |
| Full Idea: Peano Arithmetic is about any system of entities that satisfies the Peano axioms. | |
| From: report of Giuseppe Peano (Principles of Arithmetic, by a new method [1889], 6.3) by David Bostock - Philosophy of Mathematics 6.3 | |
| A reaction: This doesn't sound like numbers in the fullest sense, since those should facilitate counting objects. '3' should mean that number of rose petals, and not just a position in a well-ordered series. |
| 17634 | Peano axioms not only support arithmetic, but are also fairly obvious [Peano, by Russell] |
| Full Idea: Peano's premises are recommended not only by the fact that arithmetic follows from them, but also by their inherent obviousness. | |
| From: report of Giuseppe Peano (Principles of Arithmetic, by a new method [1889], p.276) by Bertrand Russell - Regressive Method for Premises in Mathematics p.276 |
| 15653 | We can add Reflexion Principles to Peano Arithmetic, which assert its consistency or soundness [Halbach on Peano] |
| Full Idea: Peano Arithmetic cannot derive its own consistency from within itself. But it can be strengthened by adding this consistency statement or by stronger axioms (particularly ones partially expressing soundness). These are known as Reflexion Principles. | |
| From: comment on Giuseppe Peano (Principles of Arithmetic, by a new method [1889], 1.2) by Volker Halbach - Axiomatic Theories of Truth (2005 ver) 1.2 |
| 10216 | We master arithmetic by knowing all the numbers in our soul [Plato] |
| Full Idea: It must surely be true that a man who has completely mastered arithmetic knows all numbers? Because there are pieces of knowledge covering all numbers in his soul. | |
| From: Plato (Theaetetus [c.368 BCE], 198b) | |
| A reaction: This clearly views numbers as objects. Expectation of knowing them all is a bit startling! They also appear to be innate in us, and hence they appear to be Forms. See Aristotle's comment in Idea 645. |
| 17635 | Arithmetic can have even simpler logical premises than the Peano Axioms [Russell on Peano] |
| Full Idea: Peano's premises are not the ultimate logical premises of arithmetic. Simpler premises and simpler primitive ideas are to be had by carrying our analysis on into symbolic logic. | |
| From: comment on Giuseppe Peano (Principles of Arithmetic, by a new method [1889], p.276) by Bertrand Russell - Regressive Method for Premises in Mathematics p.276 |
| 2060 | There seem to be two sorts of change: alteration and motion [Plato] |
| Full Idea: There are two kinds of change, I think: alteration and motion. | |
| From: Plato (Theaetetus [c.368 BCE], 181d) |
| 18451 | The presence of the incorporeal is only known by certain kinds of disposition [Porphyry] |
| Full Idea: Being everywhere and nowhere, the incorporeal, wherever it happens to be, betrays its presence only by a certain kind of disposition. | |
| From: Porphyry (Launching Points to the Realm of the Mind [c.280], 4Enn3 21(20)) | |
| A reaction: There is a mystical or dualist view of fundamental powers, as the spiritual engine which drives passive physical nature. It's rubbish of course, but if powers are primitive in a naturalistic theory, it is not a view which can be refuted. |
| 18459 | Diversity arises from the power of unity [Porphyry] |
| Full Idea: Diversity is born of the development of the power of unity. | |
| From: Porphyry (Launching Points to the Realm of the Mind [c.280], 6Enn5 42) | |
| A reaction: I doubt whether even Porphyry understood this, but we might say that once the principle of unification enters into nature, it will inevitably result in diversity. One all-embracing unity would be indiscernible. |
| 2084 | If a word has no parts and has a single identity, it turns out to be the same kind of thing as a letter [Plato] |
| Full Idea: If a complex or a syllable has no parts and is a single identity, hasn't it turned out to be the same kind of thing as an element or letter? | |
| From: Plato (Theaetetus [c.368 BCE], 205d) |
| 15844 | A sum is that from which nothing is lacking, which is a whole [Plato] |
| Full Idea: But this sum now - isn't it just when there is nothing lacking that it is a sum? Yes, necessarily. And won't this very same thing - that from which nothing is lacking - be a whole? | |
| From: Plato (Theaetetus [c.368 BCE], 205a) | |
| A reaction: This seems to be right, be rather too vague and potentially circular to be of much use. What is the criterion for deciding that nothing is lacking? |
| 15843 | The whole can't be the parts, because it would be all of the parts, which is the whole [Plato] |
| Full Idea: The whole does not consist of parts; for it did, it would be all the parts and so would be the sum. | |
| From: Plato (Theaetetus [c.368 BCE], 204e) | |
| A reaction: That is, 'the whole is the sum of its parts' is a tautology! The claim that 'the whole is more than the sum of its parts' gets into similar trouble. See Verity Harte on this. |
| 2080 | Things are only knowable if a rational account (logos) is possible [Plato] |
| Full Idea: Things which are susceptible to a rational account are knowable. | |
| From: Plato (Theaetetus [c.368 BCE], 201d) |
| 16126 | Expertise is knowledge of the whole by means of the parts [Plato] |
| Full Idea: A man has passed from mere judgment to expert knowledge of the being of a wagon when he has done so in virtue of having gone over the whole by means of the elements. | |
| From: Plato (Theaetetus [c.368 BCE], 207c) | |
| A reaction: Plato is emphasising that the expert must know the hundred parts of a wagon, and not just the half dozen main components, but here the point is to go over the whole via the parts, and not just list the parts. |
| 2050 | It is impossible to believe something which is held to be false [Plato] |
| Full Idea: It is impossible to believe something which is not the case. | |
| From: Plato (Theaetetus [c.368 BCE], 167a) |
| 2076 | How can a belief exist if its object doesn't exist? [Plato] |
| Full Idea: If the object of a belief is what is not, the object of this belief is nothing; but if there is no object to a belief, then that is not belief at all. | |
| From: Plato (Theaetetus [c.368 BCE], 189a) |
| 2045 | Perception is infallible, suggesting that it is knowledge [Plato] |
| Full Idea: Perception is always of something that is, and it is infallible, which suggests that it is knowledge. | |
| From: Plato (Theaetetus [c.368 BCE], 152c) |
| 2067 | Our senses could have been separate, but they converge on one mind [Plato] |
| Full Idea: It would be peculiar if each of us were like a Trojan horse, with a whole bunch of senses sitting inside us, rather than that all these perceptions converge onto a single identity (mind, or whatever one ought to call it). | |
| From: Plato (Theaetetus [c.368 BCE], 184d) |
| 2068 | With what physical faculty do we perceive pairs of opposed abstract qualities? [Plato] |
| Full Idea: With what physical faculty do we perceive being and not-being, similarity and dissimilarity, identity and difference, oneness and many, odd and even and other maths, ….fineness and goodness? | |
| From: Plato (Theaetetus [c.368 BCE], 185d) |
| 2078 | You might mistake eleven for twelve in your senses, but not in your mind [Plato] |
| Full Idea: Sight or touch might make someone take eleven for twelve, but he could never form this mistaken belief about the contents of his mind. | |
| From: Plato (Theaetetus [c.368 BCE], 195e) |
| 2069 | Thought must grasp being itself before truth becomes possible [Plato] |
| Full Idea: If you can't apprehend being you can't apprehend truth, and so a thing could not be known. Therefore knowledge is not located in immediate experience but in thinking about it, since the latter makes it possible to grasp being and truth. | |
| From: Plato (Theaetetus [c.368 BCE], 186c) |
| 18452 | Memory is not conserved images, but reproduction of previous thought [Porphyry] |
| Full Idea: Memory does not consist in preserving images. It is a faculty of reproducing the conceptions with which our soul has been occupied. | |
| From: Porphyry (Launching Points to the Realm of the Mind [c.280], 5Enn6 25(2)) |
| 2089 | An inadequate rational account would still not justify knowledge [Plato] |
| Full Idea: If you don't know which letters belong together in the right syllables…it is possible for true belief to be accompanied by a rational account and still not be entitled to the name of knowledge. | |
| From: Plato (Theaetetus [c.368 BCE], 208b) | |
| A reaction: In each case of justification there is a 'clinching' stage, for which there is never going to be a strict rule. It might be foundational, but equally it might be massive coherence, or no alternative. |
| 2085 | Parts and wholes are either equally knowable or equally unknowable [Plato] |
| Full Idea: Either a syllable and its letters are equally knowable and expressible in a rational account, or they are both equally unknowable and inexpressible. | |
| From: Plato (Theaetetus [c.368 BCE], 205e) | |
| A reaction: Presumably you could explain the syllable by the letters, but not vice versa, but he must mean that the explanation is worthless without the letters being explained too. So all explanation is worthless? |
| 2091 | Without distinguishing marks, how do I know what my beliefs are about? [Plato] |
| Full Idea: If I only have beliefs about Theaetetus when I don't know his distinguishing mark, how on earth were my beliefs about you rather than anyone else? | |
| From: Plato (Theaetetus [c.368 BCE], 209b) | |
| A reaction: This is a rather intellectualist approach to mental activity. Presumably Theaetetus has lots of distinguishing marks, but they are not conscious. Must Socrates know everything? |
| 2087 | A rational account might be seeing an image of one's belief, like a reflection in a mirror [Plato] |
| Full Idea: A rational account might be forming an image of one's belief, as in a mirror or a pond. | |
| From: Plato (Theaetetus [c.368 BCE], 206d) | |
| A reaction: Not promising, since the image is not going to be clearer than the original, or contain any new information. Maybe it would be clarified by being 'framed', instead of drifting in muddle. |
| 2090 | A rational account involves giving an image, or analysis, or giving a differentiating mark [Plato] |
| Full Idea: A third sort of rational account (after giving an image, or analysing elements) is being able to mention some mark which differentiates the object in question ('the sun is the brightest heavenly body'). | |
| From: Plato (Theaetetus [c.368 BCE], 208c) | |
| A reaction: This is Plato's clearest statement of what would be involved in adding the necessary logos to your true belief. An image of it, or an analysis, or an individuation. How about a cause? |
| 2081 | Maybe primary elements can be named, but not receive a rational account [Plato] |
| Full Idea: Maybe the primary elements of which things are composed are not susceptible to rational accounts. Each of them taken by itself can only be named, but nothing further can be said about it. | |
| From: Plato (Theaetetus [c.368 BCE], 201e) | |
| A reaction: This still seems to be more or less the central issue in philosophy - which things should be treated as 'primitive', and which other things are analysed and explained using the primitive tools? |
| 2088 | A rational account of a wagon would mean knowledge of its hundred parts [Plato] |
| Full Idea: In the case of a wagon, we may only have correct belief, but someone who is able to explain what it is by going through its hundred parts has got hold of a rational account. | |
| From: Plato (Theaetetus [c.368 BCE], 207b) | |
| A reaction: A wonderful example. In science, you know smoking correlates with cancer, but you only know it when you know the mechanism, the causal structure. This may be a general truth. |
| 2047 | What evidence can be brought to show whether we are dreaming or not? [Plato] |
| Full Idea: What evidence could be brought if we were asked at this very moment whether we are asleep and are dreaming all our thoughts? | |
| From: Plato (Theaetetus [c.368 BCE], 158b) |
| 2053 | If you claim that all beliefs are true, that includes beliefs opposed to your own [Plato] |
| Full Idea: To say that everyone believes what is the case, is to concede the truth of the oppositions' beliefs; in other words, the person has to concede that he himself is wrong. | |
| From: Plato (Theaetetus [c.368 BCE], 171a) |
| 2059 | How can a relativist form opinions about what will happen in the future? [Plato] |
| Full Idea: Does a relativist have any authority to decide about things which will happen in the future? | |
| From: Plato (Theaetetus [c.368 BCE], 178c) | |
| A reaction: Nice question! It seems commonsense that such speculations are possible, but without a concept of truth they are ridiculous. |
| 2054 | Clearly some people are superior to others when it comes to medicine [Plato] |
| Full Idea: In medicine, at least, most people are not self-sufficient at prescribing and effecting cures for themselves, and here some people are superior to others. | |
| From: Plato (Theaetetus [c.368 BCE], 171e) |
| 18453 | Intelligence is aware of itself, so the intelligence is both the thinker and the thought [Porphyry] |
| Full Idea: Since intelligence is intelligible for intelligence, intelligence is its own object. ...Intelligence, therefore, is simultaneously thinker and thought, all that thinks and all that is thought. | |
| From: Porphyry (Launching Points to the Realm of the Mind [c.280], 5Enn3 32(5-7)) | |
| A reaction: This is a bit of a problem for Descartes, if the Cogito is taken as offering evidence (thought) for the existence of a thinker ('I'). Porphyry implies that the separation Descartes requires is impossible. |
| 18462 | The soul is everywhere and nowhere in the body, and must be its cause [Porphyry] |
| Full Idea: The soul is neither a body, nor in the body, but is only the cause of the body, because she is simultaneously everywhere and nowhere in the body. | |
| From: Porphyry (Launching Points to the Realm of the Mind [c.280], 6Enn5 43) | |
| A reaction: This is the rather bewildering phenomenology of consciousness which persuaded Descartes of dualism. |
| 18463 | Successful introspection reveals the substrate along with the object of thought [Porphyry] |
| Full Idea: He who by thought can penetrate within his own substance, and can thus acquire knowledge of it, finds himself in this actualisation of knowledge and consciousness, where the substrate that knows is identical with the object that is known. | |
| From: Porphyry (Launching Points to the Realm of the Mind [c.280], 6Enn5 44) | |
| A reaction: It seems remarkably that this ability is confidently asserted by Porphyry, and flatly denied by Hume. Were they just different people, or were they looking for different things, or was one of them deluded? |
| 18458 | The soul is bound to matter by the force of its own disposition [Porphyry] |
| Full Idea: The individual soul, which declines towards matter, is bound to the matter by the form which her disposition has made her choose. | |
| From: Porphyry (Launching Points to the Realm of the Mind [c.280], 6Enn4 39) | |
| A reaction: This sounds like the soul is boss over the matter, and yet the soul is 'made' to choose union with matter. The Universal Soul is seen by Porphyr as the controller of the situation. |
| 18464 | Justice is each person fulfilling his function [Porphyry] |
| Full Idea: Justice, as has been rightly said, consists in each one fulfilling his [authentic and proper] function. | |
| From: Porphyry (Launching Points to the Realm of the Mind [c.280], 6Enn5 44) | |
| A reaction: This is presumably a direct reference to the theory in Plato's 'Republic'. It makes the connection between virtue and function which I take to be basic to virtue theory, giving it a naturalistic advantaged over other theories. |
| 18448 | We should avoid the pleasures of love, or at least, should not enact our dreams [Porphyry] |
| Full Idea: The pleasures of love will not even involuntarily be tasted, at least, she will not allow herself to be drawn beyond the lights of fancy that occur in dreams. | |
| From: Porphyry (Launching Points to the Realm of the Mind [c.280], 1Enn2 I.4) | |
| A reaction: Presumably erotic dreams are only tolerated because not much can be done about them. This brings out the puritanism of neo-platonism. |
| 18444 | Civil virtues make us behave benevolently, and thereby unite citizens [Porphyry] |
| Full Idea: The object of the civil virtues is to make us benevolent in our dealings with our fellow-human beings, and are so-called because they unite citizens. | |
| From: Porphyry (Launching Points to the Realm of the Mind [c.280], 1Enn2 I.1) | |
| A reaction: Modern commentators underestimate the close link between ancient virtue and citizenship. It is hard for one person to have much of a notion of virtue if they live on a desert island, beyond caring for personal health. |
| 18445 | Civil virtues control the passions, and make us conform to our nature [Porphyry] |
| Full Idea: The civil virtues moderate the passions; their object is to teach us to live in conformity with the laws of human nature. | |
| From: Porphyry (Launching Points to the Realm of the Mind [c.280], 1Enn2 I.2) | |
| A reaction: The link with human nature is basic to virtue theory, but this proposal is rather too vague. Are passions not part of the laws of human nature? |
| 18446 | Purificatory virtues detach the soul completely from the passions [Porphyry] |
| Full Idea: The object of the 'purificatory' virtues is to detach the soul completely from the passions. | |
| From: Porphyry (Launching Points to the Realm of the Mind [c.280], 1Enn2 I.4) | |
| A reaction: This is an aspect of virtue theory which doesn't appear in Aristotle. He is in favour of rational control of the passions, but not of totally abandoning them. The neo-platonists are much more puritanical. They seem to go against human nature. |
| 18447 | There are practical, purificatory, contemplative, and exemplary virtues [Porphyry] |
| Full Idea: The practical virtues make man virtuous; the purificatory virtues make man divine....; the contemplative virtues defiy; while the exemplary virtues make a man the parent of divinities. | |
| From: Porphyry (Launching Points to the Realm of the Mind [c.280], 1Enn2 I.4) | |
| A reaction: I like the idea of the 'exemplary' virtues. I think an entire theory of morality could be built on the notion that we are all role-models for one another. |
| 18456 | Unified real existence is neither great nor small, though greatness and smallness participate in it [Porphyry] |
| Full Idea: By its identity and numerical unity, real existence is neither great nor small, neither very large nor very small, though it causes even greatest and smallest to participate in its nature. | |
| From: Porphyry (Launching Points to the Realm of the Mind [c.280], 6Enn4 37(5)) | |
| A reaction: Note the platonic word 'participate' [metechein], suggesting that he is talking about the Form of Existence here. Note also that we have 'real' existence here, implying a lesser type of existence that participates in it. |
| 18454 | Time is the circular movement of the soul [Porphyry] |
| Full Idea: It is the circular movement of the soul that constitutes time, just as the permanence of intelligence in itself constitutes eternity. | |
| From: Porphyry (Launching Points to the Realm of the Mind [c.280], 5Enn3 32(5-7)) | |
| A reaction: Plato loved circles. If you think time is subjective, this is trying to express your intuition. Personally I think it is nonsense |
| 18455 | Some think time is seen at rest, as well as in movement [Porphyry] |
| Full Idea: Some have believed that time manifested in rest as well as in movement. | |
| From: Porphyry (Launching Points to the Realm of the Mind [c.280], 5Enn3 32(5-7)) | |
| A reaction: If you like this idea, you should see Shoemaker's lovely three-worlds thought experiment. |
| 18460 | God is nowhere, and hence everywhere [Porphyry] |
| Full Idea: The divinity is everywhere because it is nowhere. | |
| From: Porphyry (Launching Points to the Realm of the Mind [c.280], 6Enn5 43) |
| 2058 | God must be the epitome of goodness, and we can only approach a divine state by being as good as possible [Plato] |
| Full Idea: It is impossible for God to be immoral and not to be the acme of morality; and the only way any of us can approximate to God is to become as moral as possible. | |
| From: Plato (Theaetetus [c.368 BCE], 176c) |
| 18461 | Everything existing proceeds from divinity, and is within divinity [Porphyry] |
| Full Idea: All things that possess or do not possess existence proceed from divinity, and are within divinity. | |
| From: Porphyry (Launching Points to the Realm of the Mind [c.280], 6Enn5 43) | |
| A reaction: Nice to see Porphyry endorsing Meinongian objects. I doubt whether he counts as a pantheist, but this is a very pantheistic remark. |
| 18449 | Nature binds or detaches body to soul, but soul itself joins and detaches soul from body [Porphyry] |
| Full Idea: Nature binds the body to the soul, but it is the soul herself that has bound herself to the body. It, therefore, belongs to nature to detach the body from the soul, while it is the soul herself that detaches herself from the body. | |
| From: Porphyry (Launching Points to the Realm of the Mind [c.280], 1Enn9 2) | |
| A reaction: Baffling. What happens if there is a conflict? I suppose either party can cancel the bargain, but who wins when they disagree? |
| 18457 | Individual souls are all connected, though distinct, and without dividing universal Soul [Porphyry] |
| Full Idea: Individual souls are distinct without being separated from each other, and without dividing the universal Soul into a number of parts; they are united to each other without becoming confused. | |
| From: Porphyry (Launching Points to the Realm of the Mind [c.280], 6Enn4 39) | |
| A reaction: This sounds like Jung's theory that there is a universal subconscious which links us all together. Taken literally, I assume it is nonsense. As an invitation to acknowledge how much we all have in common, it is a nice corrective to liberal individualism. |
| 2057 | There must always be some force of evil ranged against good [Plato] |
| Full Idea: The elimination of evil is impossible, Theodorus; there must always be some force ranged against good. | |
| From: Plato (Theaetetus [c.368 BCE], 176a) |