21 ideas
| 192 | Only one thing can be contrary to something [Plato] |
| Full Idea: To everything that admits of a contrary there is one contrary and no more. | |
| From: Plato (Protagoras [c.380 BCE], 332c) | |
| A reaction: The sort of thing for which a modern philosopher would demand a proof (and then reject when the proof couldn't be found), where a Greek is happy to assert it as self-evident. I can't think of a counterexample. |
| 9358 | There are several logics, none of which will ever derive falsehoods from truth [Lewis,CI] |
| Full Idea: The fact is that there are several logics, markedly different, each self-consistent in its own terms and such that whoever, using it, avoids false premises, will never reach a false conclusion. | |
| From: C.I. Lewis (A Pragmatic Conception of the A Priori [1923], p.366) | |
| A reaction: As the man who invented modal logic in five different versions, he speaks with some authority. Logicians now debate which version is the best, so how could that be decided? You could avoid false conclusions by never reasoning at all. |
| 9357 | Excluded middle is just our preference for a simplified dichotomy in experience [Lewis,CI] |
| Full Idea: The law of excluded middle formulates our decision that whatever is not designated by a certain term shall be designated by its negative. It declares our purpose to make a complete dichotomy of experience, ..which is only our penchant for simplicity. | |
| From: C.I. Lewis (A Pragmatic Conception of the A Priori [1923], p.365) | |
| A reaction: I find this view quite appealing. 'Look, it's either F or it isn't!' is a dogmatic attitude which irritates a lot of people, and appears to be dispensible. Intuitionists in mathematics dispense with the principle, and vagueness threatens it. |
| 9364 | Names represent a uniformity in experience, or they name nothing [Lewis,CI] |
| Full Idea: A name must represent some uniformity in experience or it names nothing. | |
| From: C.I. Lewis (A Pragmatic Conception of the A Priori [1923], p.368) | |
| A reaction: I like this because, in the quintessentially linguistic debate about the exact logical role of names, it reminds us that names arise because of the way reality is; they are not sui generis private games for logicians. |
| 190 | If asked whether justice itself is just or unjust, you would have to say that it is just [Plato] |
| Full Idea: If someone asked me 'Is justice itself just or unjust?' I should answer that it was just, wouldn't you? I agree. | |
| From: Plato (Protagoras [c.380 BCE], 330c) |
| 9362 | Necessary truths are those we will maintain no matter what [Lewis,CI] |
| Full Idea: Those laws and those laws only have necessary truth which we are prepared to maintain, no matter what. | |
| From: C.I. Lewis (A Pragmatic Conception of the A Priori [1923], p.367) | |
| A reaction: This bold and simple claim has famously been torpedoed by a well-known counterexample - that virtually every human being will cling on to the proposition "dogs have at some time existed" no matter what, but it clearly isn't a necessary truth. |
| 20184 | The only real evil is loss of knowledge [Plato] |
| Full Idea: The only real kind of faring ill is the loss of knowledge. | |
| From: Plato (Protagoras [c.380 BCE], 345b) | |
| A reaction: This must crucially involve the intellectualist view (of Socrates) that virtuos behaviour results from knowledge, and moral wickedness is the result of ignorance. It is hard to see how forgetting a phone number is evil. |
| 20185 | The most important things in life are wisdom and knowledge [Plato] |
| Full Idea: It would be shameful indeed to say that wisdom and knowledge are anything but the most powerful forces in human activity. | |
| From: Plato (Protagoras [c.380 BCE], 352d) | |
| A reaction: He lumps wisdom and knowledge together, and I think we can take 'knowledge' to mean something like understanding, because obviously mere atomistic propositional knowledge can be utterly trivial. |
| 9365 | We can maintain a priori principles come what may, but we can also change them [Lewis,CI] |
| Full Idea: The a priori contains principles which can be maintained in the face of all experience, representing the initiative of the mind. But they are subject to alteration on pragmatic grounds, if expanding experience shows their intellectual infelicity. | |
| From: C.I. Lewis (A Pragmatic Conception of the A Priori [1923], p.373) | |
| A reaction: [compressed] This simply IS Quine's famous 'web of belief' picture, showing how firmly Quine is in the pragmatist tradition. Lewis treats a priori principles as a pragmatic toolkit, which can be refined to be more effective. Not implausible... |
| 191 | Everything resembles everything else up to a point [Plato] |
| Full Idea: Everything resembles everything else up to a point. | |
| From: Plato (Protagoras [c.380 BCE], 331d) |
| 9361 | We have to separate the mathematical from physical phenomena by abstraction [Lewis,CI] |
| Full Idea: Physical processes present us with phenomena in which the purely mathematical has to be separated out by abstraction. | |
| From: C.I. Lewis (A Pragmatic Conception of the A Priori [1923], p.367) | |
| A reaction: This is the father of modal logic endorsing traditional abstractionism, it seems. He is also, though, endorsing the view that a priori knowledge is created by us, with pragmatic ends in view. |
| 21932 | 'Différance' is the interwoven history of each sign [Derrida, by Glendinning] |
| Full Idea: What Derrida calls 'différance' can be understood as the movement through which every sign is 'constituted historically as a weave of differences'....This replacement for 'speech' in the 'origin' of the system is to avoid the circularity in structuralism. | |
| From: report of Jacques Derrida (Différance [1982]) by Simon Glendinning - Derrida: A Very Short Introduction 5 | |
| A reaction: [compressed] Struggling to grasp this. Some English words entirely change their meaning over time (e.g. buxom). Does the lost meaning remain part of the new meaning? If so, how? He also calls différance 'sameness which is not identical'. |
| 203 | Courage is knowing what should or shouldn't be feared [Plato] |
| Full Idea: Knowledge of what is and is not to be feared is courage. | |
| From: Plato (Protagoras [c.380 BCE], 360d) |
| 202 | No one willingly and knowingly embraces evil [Plato] |
| Full Idea: No one willingly goes to meet evil, or what he thinks is evil. | |
| From: Plato (Protagoras [c.380 BCE], 358d) | |
| A reaction: Presumably people who actively choose satanism can override this deep-seated attitude. But their adherence to evil usually seems to be rather restrained. A danger of tautology with ideas like this. |
| 193 | Some things are good even though they are not beneficial to men [Plato] |
| Full Idea: 'Do you mean by good those things that are beneficial to men?' 'Not only those. I call some things which are not beneficial good as well'. | |
| From: Plato (Protagoras [c.380 BCE], 333e) | |
| A reaction: Examples needed, but this would be bad news for utilitarians. Good health is not seen as beneficial if it is taken for granted. Not being deaf. |
| 197 | Some pleasures are not good, and some pains are not evil [Plato] |
| Full Idea: There are some pleasures which are not good, and some pains which are not evil. | |
| From: Plato (Protagoras [c.380 BCE], 351d) | |
| A reaction: Sadism and child birth. Though Bentham (I think) says that there is nothing good about the pain, since the event would obviously be better without it. |
| 200 | People tend only to disapprove of pleasure if it leads to pain, or prevents future pleasure [Plato] |
| Full Idea: The only reason the common man disapproves of pleasures is if they lead to pain and deprive us of future pleasures. | |
| From: Plato (Protagoras [c.380 BCE], 354a) | |
| A reaction: Plato has a strong sense that some pleasures are just innately depraved and wicked. If those pleasure don't hurt anyone, it is very hard to pinpoint what is wrong with them. |
| 188 | Socrates did not believe that virtue could be taught [Plato] |
| Full Idea: Socrates: I do not believe that virtue can be taught. | |
| From: Plato (Protagoras [c.380 BCE], 320b) |
| 204 | Socrates is contradicting himself in claiming virtue can't be taught, but that it is knowledge [Plato] |
| Full Idea: Socrates is contradicting himself by saying virtue is not teachable, and yet trying to demonstrate that every virtue is knowledge. | |
| From: Plato (Protagoras [c.380 BCE], 361b) |
| 189 | If we punish wrong-doers, it shows that we believe virtue can be taught [Plato] |
| Full Idea: Athenians inflict punishment on wrong-doers, which shows that they too think it possible to impart and teach goodness. | |
| From: Plato (Protagoras [c.380 BCE], 324c) |
| 9363 | Science seeks classification which will discover laws, essences, and predictions [Lewis,CI] |
| Full Idea: The scientific search is for such classification as will make it possible to correlate appearance and behaviour, to discover law, to penetrate to the "essential nature" of things in order that behaviour may become predictable. | |
| From: C.I. Lewis (A Pragmatic Conception of the A Priori [1923], p.368) | |
| A reaction: Modern scientific essentialists no longer invoke scare quotes, and I think we should talk of the search for the 'mechanisms' which explain behaviour, but Lewis seems to have been sixty years ahead of his time. |