46 ideas
| 354 | Wisdom makes virtue and true goodness possible [Plato] |
| Full Idea: It is wisdom that makes possible courage and self-control and integrity or, in a word, true goodness. | |
| From: Plato (Phaedo [c.382 BCE], 069b) | |
| A reaction: Aristotle also says that prudence (phronesis) makes virtue possible. |
| 370 | Philosophy is a purification of the soul ready for the afterlife [Plato] |
| Full Idea: Souls which have purified themselves sufficiently by philosophy will live after death without bodies. | |
| From: Plato (Phaedo [c.382 BCE], 114b) | |
| A reaction: Purifying it of what? Error, or desire, or narrow-mindedness, or the physical? |
| 19199 | Some say metaphysics is a highly generalised empirical study of objects [Tarski] |
| Full Idea: For some people metaphysics is a general theory of objects (ontology) - a discipline which is to be developed in a purely empirical way, and which differs from other empirical disciplines in its generality. | |
| From: Alfred Tarski (The Semantic Conception of Truth [1944], 19) | |
| A reaction: Tarski says some people despise it, but for him such metaphysics is 'not objectionable'. I subscribe to this view, but the empirical aspect is very remote, because it's too general for detail observation or experiment. Generality is the key to philosophy. |
| 19193 | Disputes that fail to use precise scientific terminology are all meaningless [Tarski] |
| Full Idea: Disputes like the vague one about 'the right conception of truth' occur in all domains where, instead of exact, scientific terminology, common language with its vagueness and ambiguity is used; and they are always meaningless, and therefore in vain. | |
| From: Alfred Tarski (The Semantic Conception of Truth [1944], 14) | |
| A reaction: Taski taught a large number of famous philosophers in California in the 1950s, and this approach has had a huge influence. Recently there has been a bit of a rebellion. E.g. Kit Fine doesn't think it can all be done in formal languages. |
| 350 | In investigation the body leads us astray, but the soul gets a clear view of the facts [Plato] |
| Full Idea: When philosophers investigate with the help of the body they are led astray, but through reflection the soul gets a clear view of the facts. | |
| From: Plato (Phaedo [c.382 BCE], 065c) |
| 362 | The greatest misfortune for a person is to develop a dislike for argument [Plato] |
| Full Idea: No greater misfortune could happen to anyone than developing a dislike for argument. | |
| From: Plato (Phaedo [c.382 BCE], 089d) |
| 19179 | For a definition we need the words or concepts used, the rules, and the structure of the language [Tarski] |
| Full Idea: We must specify the words or concepts which we wish to use in defining the notion of truth; and we must also give the formal rules to which the definition should conform. More generally, we must describe the formal structure of the language. | |
| From: Alfred Tarski (The Semantic Conception of Truth [1944], 01) | |
| A reaction: This, of course, is a highly formal view of how definition should be achieved, offered in anticipation of one of the most famous definitions in logic (of truth, by Tarski). Normally we assume English and classical logic. |
| 19178 | Definitions of truth should not introduce a new version of the concept, but capture the old one [Tarski] |
| Full Idea: The desired definition of truth does not aim to specify the meaning of a familiar word used to denote a novel notion; on the contrary, it aims to catch hold of the actual meaning of an old notion. | |
| From: Alfred Tarski (The Semantic Conception of Truth [1944], 01) | |
| A reaction: Tarski refers back to Aristotle for an account of the 'old notion'. To many the definition of Tarski looks very weird, so it is important to see that he is trying to capture the original concept. |
| 19177 | A definition of truth should be materially adequate and formally correct [Tarski] |
| Full Idea: The main problem of the notion of truth is to give a satisfactory definition which is materially adequate and formally correct. | |
| From: Alfred Tarski (The Semantic Conception of Truth [1944], 01) | |
| A reaction: That is, I take it, that it covers all cases of being true and failing to be true, and it fits in with the logic. The logic is explicitly classical logic, and he is not aiming to give the 'nature' or natural language understanding of the concept. |
| 19186 | A rigorous definition of truth is only possible in an exactly specified language [Tarski] |
| Full Idea: The problem of the definition of truth obtains a precise meaning and can be solved in a rigorous way only for those languages whose structure has been exactly specified. | |
| From: Alfred Tarski (The Semantic Conception of Truth [1944], 06) | |
| A reaction: Taski has just stated how to exactly specify the structure of a language. He says definition can only be vague and approximate for natural languages. (The usual criticism of the correspondence theory is its vagueness). |
| 19194 | We may eventually need to split the word 'true' into several less ambiguous terms [Tarski] |
| Full Idea: A time may come when we find ourselves confronted with several incompatible, but equally clear and precise, conceptions of truth. It will then become necessary to abandon the ambiguous usage of the word 'true', and introduce several terms instead. | |
| From: Alfred Tarski (The Semantic Conception of Truth [1944], 14) | |
| A reaction: There may be a whiff of the pragmatic attitude to truth here, though that view is not necessarily pluralist. Analytic philosophy needs much more splitting of difficult terms into several more focused terms. |
| 19180 | It is convenient to attach 'true' to sentences, and hence the language must be specified [Tarski] |
| Full Idea: For several reasons it appears most convenient to apply the term 'true' to sentences, and we shall follow this course. Consequently, we must always relate the notion of truth, like that of a sentence, to a specific language. | |
| From: Alfred Tarski (The Semantic Conception of Truth [1944], 02) | |
| A reaction: Personally I take truth to attach to propositions, since sentences are ambiguous. In Idea 17308 the one sentence expresses three different truths (in my opinion), even though a single sentence (given in the object language) specifies it. |
| 19181 | In the classical concept of truth, 'snow is white' is true if snow is white [Tarski] |
| Full Idea: If we base ourselves on the classical conception of truth, we shall say that the sentence 'snow is white' is true if snow is white, and it is false if snow is not white. | |
| From: Alfred Tarski (The Semantic Conception of Truth [1944], 04) | |
| A reaction: I had not realised, prior to his, how closely Tarski is sticking to Aristotle's famous formulation of truth. The point is that you can only specify 'what is' using a language. Putting 'true' in the metalanguage gives specific content to Aristotle. |
| 19196 | Scheme (T) is not a definition of truth [Tarski] |
| Full Idea: It is a mistake to regard scheme (T) as a definition of truth. | |
| From: Alfred Tarski (The Semantic Conception of Truth [1944], 15) | |
| A reaction: The point is, I take it, that the definition is the multitude of sentences which are generated by the schema, not the schema itself. |
| 19183 | Each interpreted T-sentence is a partial definition of truth; the whole definition is their conjunction [Tarski] |
| Full Idea: In 'X is true iff p' if we replace X by the name of a sentence and p by a particular sentence this can be considered a partial definition of truth. The whole definition has to be ...a logical conjunction of all these partial definitions. | |
| From: Alfred Tarski (The Semantic Conception of Truth [1944], 04) | |
| A reaction: This seems an unprecedented and odd way to define something. Define 'red' by '"This tomato is red" iff this tomato is red', etc? Define 'stone' by collecting together all the stones? The complex T-sentences are infinite in number. |
| 19182 | Use 'true' so that all T-sentences can be asserted, and the definition will then be 'adequate' [Tarski] |
| Full Idea: We wish to use the term 'true' in such a way that all the equivalences of the form (T) [i.e. X is true iff p] can be asserted, and we shall call a definition of truth 'adequate' if all these equivalences follow from it. | |
| From: Alfred Tarski (The Semantic Conception of Truth [1944], 04) | |
| A reaction: The interpretation of Tarski's theory is difficult. From this I'm thinking that 'true' is simply being defined as 'assertible'. This is the status of each line in a logical proof, if there is a semantic dimension to the proof (and not mere syntax). |
| 19198 | We don't give conditions for asserting 'snow is white'; just that assertion implies 'snow is white' is true [Tarski] |
| Full Idea: Semantic truth implies nothing regarding the conditions under which 'snow is white' can be asserted. It implies only that, whenever we assert or reject this sentence, we must be ready to assert or reject the correlated sentence '"snow is white" is true'. | |
| From: Alfred Tarski (The Semantic Conception of Truth [1944], 18) | |
| A reaction: This appears to identify truth with assertibility, which is pretty much what modern pragmatists say. How do you distinguish 'genuine' assertion from rhetorical, teasing or lying assertions? Genuine assertion implies truth? Hm. |
| 19184 | The best truth definition involves other semantic notions, like satisfaction (relating terms and objects) [Tarski] |
| Full Idea: It turns out that the simplest and most natural way of obtaining an exact definition of truth is one which involves the use of other semantic notions, e.g. the notion of satisfaction (...which expresses relations between expressions and objects). | |
| From: Alfred Tarski (The Semantic Conception of Truth [1944], 05) | |
| A reaction: While the T-sentences appear to be 'minimal' and 'deflationary', it seems important to remember that 'satisfaction', which is basic to his theory, is a very robust notion. He actually mentions 'objects'. But see Idea 19185. |
| 19191 | Specify satisfaction for simple sentences, then compounds; true sentences are satisfied by all objects [Tarski] |
| Full Idea: To define satisfaction we indicate which objects satisfy the simplest sentential functions, then state the conditions for compound functions. This applies automatically to sentences (with no free variables) so a true sentence is satisfied by all objects. | |
| From: Alfred Tarski (The Semantic Conception of Truth [1944], 11) | |
| A reaction: I presume nothing in the domain of objects can conflict with a sentence that has been satisfied by some of them, so 'all' the objects satisfy the sentence. Tarski doesn't use the word 'domain'. Basic satisfaction seems to be stipulated. |
| 19188 | We can't use a semantically closed language, or ditch our logic, so a meta-language is needed [Tarski] |
| Full Idea: In a 'semantically closed' language all sentences which determine the adequate usage of 'true' can be asserted in the language. ...We can't change our logic, so we reject such languages. ...So must use two different languages to discuss truth. | |
| From: Alfred Tarski (The Semantic Conception of Truth [1944], 08-09) | |
| A reaction: This section explains why a meta-language is required. It rests entirely on the existence of the Liar paradox is a semantically closed language. |
| 19189 | The metalanguage must contain the object language, logic, and defined semantics [Tarski] |
| Full Idea: Every sentence which occurs in the object language must also occur in the metalanguage, or can be translated into the metalanguage. There must also be logical terms, ...and semantic terms can only be introduced in the metalanguage by definition. | |
| From: Alfred Tarski (The Semantic Conception of Truth [1944], 09) | |
| A reaction: He suggest that if the languages are 'typed', the meta-languag, to be 'richer', must contain variables of a higher logica type. Does this mean second-order logic? |
| 10824 | If listing equivalences is a reduction of truth, witchcraft is just a list of witch-victim pairs [Field,H on Tarski] |
| Full Idea: By similar standards of reduction to Tarski's, one might prove witchcraft compatible with physicalism, as long as witches cast only a finite number of spells. We merely list witch-and-victim pairs, with no mention of the terms of witchcraft theory. | |
| From: comment on Alfred Tarski (The Semantic Conception of Truth [1944], 04) by Hartry Field - Tarski's Theory of Truth §4 |
| 19190 | We need an undefined term 'true' in the meta-language, specified by axioms [Tarski] |
| Full Idea: We have to include the term 'true', or some other semantic term, in the list of undefined terms of the meta-language, and to express fundamental properties of the notion of truth in a series of axioms. | |
| From: Alfred Tarski (The Semantic Conception of Truth [1944], 10) | |
| A reaction: It sounds as if Tarski semantic theory gives truth for the object language, but then an axiomatic theory of truth is also needed for the metalanguage. Halbch and Horsten seem to want an axiomatic theory in the object language. |
| 19197 | Truth can't be eliminated from universal claims, or from particular unspecified claims [Tarski] |
| Full Idea: Truth can't be eliminated from universal statements saying all sentences of a certain type are true, or from the proof that 'all consequences of true sentences are true'. It is also needed if we can't name the sentence ('Plato's first sentence is true'). | |
| From: Alfred Tarski (The Semantic Conception of Truth [1944], 16) | |
| A reaction: This points to the deflationary view of truth, if its only role is in talking about other sentences in this way. Tarski gives the standard reason for rejecting the Redundancy view. |
| 19185 | Semantics is a very modest discipline which solves no real problems [Tarski] |
| Full Idea: Semantics as it is conceived in this paper is a sober and modest discipline which has no pretensions to being a universal patent-medicine for all the ills and diseases of mankind, whether imaginary or real. | |
| From: Alfred Tarski (The Semantic Conception of Truth [1944], 05) | |
| A reaction: Written in 1944. This remark encourages the minimal or deflationary interpretation of his theory of truth, but see the robust use of 'satisfaction' in Idea 19184. |
| 19195 | Truth tables give prior conditions for logic, but are outside the system, and not definitions [Tarski] |
| Full Idea: Logical sentences are often assigned preliminary conditions under which they are true or false (often given as truth tables). However, these are outside the system of logic, and should not be regarded as definitions of the terms involved. | |
| From: Alfred Tarski (The Semantic Conception of Truth [1944], 15) | |
| A reaction: Hence, presumably, the connectives are primitives (with no nature or meaning), and the truth tables are axioms for their use? This opinion of Tarski's may have helped shift the preference towards natural deduction introduction and elimination rules. |
| 19192 | The truth definition proves semantic contradiction and excluded middle laws (not the logic laws) [Tarski] |
| Full Idea: With our definition of truth we can prove the laws of contradiction and excluded middle. These semantic laws should not be identified with the related logical laws, which belong to the sentential calculus, and do not involve 'true' at all. | |
| From: Alfred Tarski (The Semantic Conception of Truth [1944], 12) | |
| A reaction: Very illuminating. I wish modern thinkers could be so clear about this matter. The logic contains 'P or not-P'. The semantics contains 'P is either true or false'. Critics say Tarski has presupposed 'classical' logic. |
| 19187 | The Liar makes us assert a false sentence, so it must be taken seriously [Tarski] |
| Full Idea: In my judgement, it would be quite wrong and dangerous from the point of view of scientific progress to depreciate the importance of nhtinomies like the Liar Paradox, and treat them as jokes. The fact is we have been compelled to assert a false sentence. | |
| From: Alfred Tarski (The Semantic Conception of Truth [1944], 07) | |
| A reaction: This is the heartfelt cry of the perfectionist, who wants everything under control. It was the dream of the age of Frege to Hilbert, which gradually eroded after Gödel's Incompleteness proof. Short ordinary folk panic about the Liar? |
| 13155 | If you add one to one, which one becomes two, or do they both become two? [Plato] |
| Full Idea: I cannot convince myself that when you add one to one either the first or the second one becomes two, or they both become two by the addition of the one to the other, ...or that when you divide one, the cause of becoming two is now the division. | |
| From: Plato (Phaedo [c.382 BCE], 097d) | |
| A reaction: Lovely questions, all leading to the conclusion that two consists of partaking in duality, to which you can come by several different routes. |
| 21347 | If Simmias is taller than Socrates, that isn't a feature that is just in Simmias [Plato] |
| Full Idea: When you say Simmias is taller than Socrates but shorter than Phaedo, so you mean there is in Simmias both tallness and shortness? - I do. ...But surely he is not taller than Socrates because he is Simmias but because of the tallness he happens to have? | |
| From: Plato (Phaedo [c.382 BCE], 102b-c) | |
| A reaction: He adds that both people must be cited. This appears to be what we now call a rejection relative height as an 'internal' relation, which is it would presumably be if it was a feature of one or of both men. |
| 360 | We must have a prior knowledge of equality, if we see 'equal' things and realise they fall short of it [Plato] |
| Full Idea: We must have some previous knowledge of equality, before the time when we saw equal things, but realised that they fell short of it. | |
| From: Plato (Phaedo [c.382 BCE], 075a) |
| 1 | There is only one source for all beauty [Plato] |
| Full Idea: If anything is beautiful other than beauty itself, it is beautiful for no other reason but because it participates in that beautiful. | |
| From: Plato (Phaedo [c.382 BCE], 100c) | |
| A reaction: The Greek word will be 'kalon' (beautiful, fine, noble). Like Aristotle, I find it baffling that such diversity could have a single source. Beautiful things have diverse aims. |
| 368 | Other things are named after the Forms because they participate in them [Plato] |
| Full Idea: The reason why other things are called after the forms is that they participate in the forms. | |
| From: Plato (Phaedo [c.382 BCE], 102a) |
| 16516 | The ship which Theseus took to Crete is now sent to Delos crowned with flowers [Plato] |
| Full Idea: The day before the trial the prow of the ship that the Athenians send to Delos had been crowned with garlands. - Which ship is that? - It is the ship in which, the Athenians say, Theseus once sailed to Crete, taking the victims. | |
| From: Plato (Phaedo [c.382 BCE], 058a) | |
| A reaction: Not philosophical, but this is the Ship of Theseus whose subsequent identity, Plutarch tells us, became a matter of dispute. |
| 357 | People are obviously recollecting when they react to a geometrical diagram [Plato] |
| Full Idea: The way in which people react to a geometrical diagram or anything like that is unmistakable proof of the theory of recollection. | |
| From: Plato (Phaedo [c.382 BCE], 073a) |
| 359 | If we feel the inadequacy of a resemblance, we must recollect the original [Plato] |
| Full Idea: If someone sees a resemblance, but feels that it falls far short of the original, they must therefore have a recollection of the original. | |
| From: Plato (Phaedo [c.382 BCE], 074e) |
| 9343 | To achieve pure knowledge, we must get rid of the body and contemplate things with the soul [Plato] |
| Full Idea: We are convinced that if we are ever to have pure knowledge of anything, we must get rid of the body and contemplate things by themselves with the soul by itself. | |
| From: Plato (Phaedo [c.382 BCE], 066c) | |
| A reaction: This seems to be the original ideal which motivates the devotion to a priori knowledge - that it will lead to a 'pure' knowledge, which in Plato's case will be eternal and necessary knowledge, like taking lessons from the gods. Wrong. |
| 15859 | To investigate the causes of things, study what is best for them [Plato] |
| Full Idea: If one wished to know the cause of each thing, why it comes to be or perishes or exists, one had to find what was the best way for it to be, or to be acted upon, or to act. Then it befitted a man to investigate only ...what is best. | |
| From: Plato (Phaedo [c.382 BCE], 097d) | |
| A reaction: A reversal of the modern idea of 'best explanation'. Socrates is citing Anaxagoras's proposal to understand things by interpreting the workings of a supreme Mind. It is the religious version of best explanation. |
| 13154 | Do we think and experience with blood, air or fire, or could it be our brain? [Plato] |
| Full Idea: Is it with the blood that we think, or with the air or the fire that is in us? Or is it none of these, but the brain that supplies our senses of hearing and sight and smell. | |
| From: Plato (Phaedo [c.382 BCE], 097a) | |
| A reaction: In retrospect it seems surprising that such clever people hadn't worked this one out, given the evidence of anatomy, in animals and people, and given brain injuries. By the time of Galen they appear to have got the answer. |
| 364 | One soul can't be more or less of a soul than another [Plato] |
| Full Idea: Is one soul, even minutely, more or less of a soul than another? Not in the least. | |
| From: Plato (Phaedo [c.382 BCE], 093b) | |
| A reaction: This idea is attractive because unconsciousness and death seem to be abrupt procedures, and so appear to be all-or-nothing, but I would personally view extreme Alzheimer's as an erasing of the soul, though a minimum level of it seems all-or-nothing. |
| 19087 | The meaning or purport of a symbol is all the rational conduct it would lead to [Peirce] |
| Full Idea: The entire intellectual purport of any symbol consists in the total of all modes of rational conduct which, conditionally upon all the possible different circumstances and desires, would ensue upon the acceptance of the symbol. | |
| From: Charles Sanders Peirce (Issues of Pragmaticism [1905], EP ii.246), quoted by Danielle Macbeth - Pragmatism and Objective Truth p.169 n1 | |
| A reaction: Macbeth says pragmatism is founded on this theory of meaning, rather than on a theory of truth. I don't see why the causes of a symbol shouldn't be as much a part of its meaning as the consequences are. |
| 361 | It is a mistake to think that the most violent pleasure or pain is therefore the truest reality [Plato] |
| Full Idea: When anyone's soul feels a keen pleasure or pain it cannot help supposing that whatever causes the most violent emotion is the plainest and truest reality - which it is not. | |
| From: Plato (Phaedo [c.382 BCE], 084c) | |
| A reaction: Do people think that? Most people distinguish subjective from objective. Wounded soldiers are also aware of victory or defeat. |
| 351 | War aims at the acquisition of wealth, because we are enslaved to the body [Plato] |
| Full Idea: All wars are undertaken for the acquisition of wealth, and we want this because of the body, to which we are slave. | |
| From: Plato (Phaedo [c.382 BCE], 066c) |
| 13156 | Fancy being unable to distinguish a cause from its necessary background conditions! [Plato] |
| Full Idea: Fancy being unable to distinguish between the cause of a thing, and the condition without which it could not be a cause. | |
| From: Plato (Phaedo [c.382 BCE], 099c) | |
| A reaction: Not as simple as he thinks. It seems fairly easy to construct a case where the immediately impacting event remains constant, and the background condition is changed. Even worse when negligence is held to be the cause. |
| 369 | If the Earth is spherical and in the centre, it is kept in place by universal symmetry, not by force [Plato] |
| Full Idea: If the earth is spherical and in the middle of the heavens, it needs neither air nor force to keep it from falling. The uniformity of heaven and equilibrium of earth are sufficient support. | |
| From: Plato (Phaedo [c.382 BCE], 108e) |
| 363 | Whether the soul pre-exists our body depends on whether it contains the ultimate standard of reality [Plato] |
| Full Idea: The theory that our soul exists even before it enters the body surely stands or falls with the soul's possession of the ultimate standard of reality. | |
| From: Plato (Phaedo [c.382 BCE], 092d) |