34 ideas
| 8092 | Logic was merely a branch of rhetoric until the scientific 17th century [Devlin] |
| Full Idea: Until the rise of what we call the scientific method in the seventeenth century, logic was regarded largely as one aspect of rhetoric - a study of how one person't argument could convince another. | |
| From: Keith Devlin (Goodbye Descartes [1997], Ch.11) | |
| A reaction: This may well give the main reason why the Greeks invented logic in the first place. Aristotle wrote a book on rhetoric, and that was where the money was. Leibniz is clearly a key figure in the change of attitude. |
| 8081 | 'No councillors are bankers' and 'All bankers are athletes' implies 'Some athletes are not councillors' [Devlin] |
| Full Idea: Most people find it hard to find any conclusion that fits the following premises: 'No councillors are bankers', and 'All bankers are athletes'. There is a valid conclusion ('Some athletes are not councillors') but it takes quite an effort to find it. | |
| From: Keith Devlin (Goodbye Descartes [1997], Ch. 2) | |
| A reaction: A nice illustration of the fact that syllogistic logic is by no means automatic and straightforward. There is a mechanical procedure, but a lot of intuition and common sense is also needed. |
| 8085 | Modern propositional inference replaces Aristotle's 19 syllogisms with modus ponens [Devlin] |
| Full Idea: Where Aristotle had 19 different inference rules (his valid syllogisms), modern propositional logic carries out deductions using just one rule of inference: modus ponens. | |
| From: Keith Devlin (Goodbye Descartes [1997], Ch. 4) | |
| A reaction: At first glance it sounds as if Aristotle's guidelines might be more useful than the modern one, since he tells you something definite and what implies what, where modus ponens just seems to define the word 'implies'. |
| 8086 | Predicate logic retains the axioms of propositional logic [Devlin] |
| Full Idea: Since predicate logic merely extends propositional logic, all the axioms of propositional logic are axioms of predicate logic. | |
| From: Keith Devlin (Goodbye Descartes [1997], Ch. 4) | |
| A reaction: See Idea 7798 for the axioms. |
| 8091 | Situation theory is logic that takes account of context [Devlin] |
| Full Idea: In many respects, situation theory is an extension of classical logic that takes account of context. | |
| From: Keith Devlin (Goodbye Descartes [1997], Ch. 8) | |
| A reaction: John Barwise is cited as the parent of this movement. Many examples show that logical form is very hard to pin down, because word-meaning depends on context (e.g. 'several crumbs' differs from 'several mountains'). |
| 8087 | Golden ages: 1900-1960 for pure logic, and 1950-1985 for applied logic [Devlin] |
| Full Idea: The period from 1900 to about 1960 could be described as the golden age of 'pure' logic, and 1950 to 1985 the golden age of 'applied' logic (e.g. applied to everyday reasoning, and to theories of language). | |
| From: Keith Devlin (Goodbye Descartes [1997], Ch. 4) | |
| A reaction: Why do we always find that we have just missed the Golden Age? However this supports the uneasy feeling that the golden age for all advances in human knowledge is just coming to an end. Biology, including the brain, is the last frontier. |
| 8089 | Montague's intensional logic incorporated the notion of meaning [Devlin] |
| Full Idea: Montague's intensional logic was the first really successful attempt to develop a mathematical framework that incorporates the notion of meaning. | |
| From: Keith Devlin (Goodbye Descartes [1997], Ch. 8) | |
| A reaction: Previous logics, led by Tarski, had flourished by sharply dividing meaning from syntax, and concentrating on the latter. |
| 8082 | Where a conditional is purely formal, an implication implies a link between premise and conclusion [Devlin] |
| Full Idea: Implication involves some form of link or causality between the antecedent and the consequent of an if-then; normally it says that the conclusion is a consequence of the premise (where conditionals are just defined by 'true' and 'false'). | |
| From: Keith Devlin (Goodbye Descartes [1997], Ch. 2) | |
| A reaction: This distinction is a key one when discussing 'If-then' sentences. Some are merely formal conditionals, but others make real claims about where you can get to from where you are. |
| 8072 | Sentences of apparent identical form can have different contextual meanings [Devlin] |
| Full Idea: "Safety goggles must be worn in the building" is clear enough, but "dogs must always be carried on the escalator" doesn't require us to head off in search of a dog. | |
| From: Keith Devlin (Goodbye Descartes [1997], Ch. 1) | |
| A reaction: A nice illustration of how the requirements of logical form will often take us beyond the strict and literal meaning of a sentence, into context, tone, allusion and subjective aspects. |
| 8075 | Space and time are atomic in the arrow, and divisible in the tortoise [Devlin] |
| Full Idea: The arrow paradox starts with the assumption that space and time are atomic; the tortoise starts with the opposite assumption that space and time are infinitely divisible. | |
| From: Keith Devlin (Goodbye Descartes [1997], Ch. 2) | |
| A reaction: Aquinas similarly covers all options (the cosmos has a beginning, or no beginning). The nature of movement in a space which involves quantum leaps remains metaphysically puzzling. Where is a particle at half of the Planck time? |
| 8088 | People still say the Hopi have no time concepts, despite Whorf's later denial [Devlin] |
| Full Idea: The Hopi time myth does not appear to have been stopped for a moment by the fact that Whorf himself subsequently wrote that the Hopi language does indeed have words for past, present, and future | |
| From: Keith Devlin (Goodbye Descartes [1997], Ch. 5) | |
| A reaction: Arguments for relativism based on the Hopi seem now to be thoroughly discredited. Sensible people never believed them in the first place. |
| 8073 | How do we parse 'time flies like an arrow' and 'fruit flies like an apple'? [Devlin] |
| Full Idea: How do people identify subject and verb in the sentences "time flies like an arrow" and "fruit flies like an apple"? | |
| From: Keith Devlin (Goodbye Descartes [1997], Ch. 1) | |
| A reaction: A nice illustration of the fact that even if we have an innate syntax mechanism, it won't work without some semantics, and some experience of the environmental context of utterances. |
| 8076 | The distinction between sentences and abstract propositions is crucial in logic [Devlin] |
| Full Idea: The distinction between sentences and the abstract propositions that they express is one of the key ideas of logic. A logical argument consists of propositions, assembled together in a systematic fashion. | |
| From: Keith Devlin (Goodbye Descartes [1997], Ch. 2) | |
| A reaction: He may claim that arguments consist of abstract propositions, but they always get expressed in sentences. However, the whole idea of logical form implies the existence of propositions - there is something which a messy sentence 'really' says. |
| 5845 | Niceratus learnt the whole of Homer by heart, as a guide to goodness [Xenophon] |
| Full Idea: Niceratus said that his father, because he was concerned to make him a good man, made him learn the whole works of Homer, and he could still repeat by heart the entire 'Iliad' and 'Odyssey'. | |
| From: Xenophon (Symposium [c.391 BCE], 3.5) | |
| A reaction: This clearly shows the status which Homer had in the teaching of morality in the time of Socrates, and it is precisely this acceptance of authority which he was challenging, in his attempts to analyse the true basis of virtue |
| 23125 | Most good social changes are incremental, rather than revolutionary [Gopnik] |
| Full Idea: More permanent positive social change is made incrementally rather than by revolutionary transformation. | |
| From: Adam Gopnik (A Thousand Small Sanities [2019], 1) | |
| A reaction: This is the standard liberal response to revolution. Revolutionaries obviously consider such a claim to be very naïve, and a failure to grasp how deep the changes need to go. |
| 23126 | Conservatives often want peace, prosperity and tolerance, but not social fairness [Gopnik] |
| Full Idea: Many conservatives want their world to be peaceful, properous, and pluralist, just as liberals do, but they don't particularly care that it be fair. | |
| From: Adam Gopnik (A Thousand Small Sanities [2019], 1) | |
| A reaction: Every conservative will have a sense of what is fair (such as appropriate punishments, and keeping of contracts), but they are more inclined to think that fairness must be fought for by individuals, not imposed by governments. |
| 23132 | Conservatives believe obedience and rank are essential to social order [Gopnik] |
| Full Idea: The idea that the appearance of submission and obedience and rank are essential to order is at the heart of the conservative ideal. | |
| From: Adam Gopnik (A Thousand Small Sanities [2019], 2) | |
| A reaction: [He has just quoted Edmund Burke writing of Marie Antoinette] I once heard Richard Hare say that he thought social order would be best modelled on the army. A colleague once told me that obedience is a prime duty of a school teacher. |
| 23128 | The opposite of liberalism is dogmatism [Gopnik] |
| Full Idea: The opposite of liberalism is not conservatism but dogmatism. | |
| From: Adam Gopnik (A Thousand Small Sanities [2019], 1) | |
| A reaction: Nice. It pinpoints the liberal opposition to both extremes of normal politics. It might make anarchists their allies, though! |
| 23142 | People are fallible, so liberalism tries to distribute power [Gopnik] |
| Full Idea: Liberalism makes the idea of fallibility into a political practice by trying not to have too much power concentrated in one place or part of the system. | |
| From: Adam Gopnik (A Thousand Small Sanities [2019], 3) | |
| A reaction: There is a potential inefficiency and failure to focus on key goals implicit in this aim. It may be a good idea for a peacetime democracy, but a terrible idea for a wartime army. To stop corruption, don't let anyone do anything? |
| 23143 | Liberals have tried very hard to build a conscience into their institutions [Gopnik] |
| Full Idea: What liberalism can say on its own behalf is that no system of power in human history has tried harder to insert a corrective conscience into its institutions. | |
| From: Adam Gopnik (A Thousand Small Sanities [2019], 3) | |
| A reaction: What we are learning in recent years is that wonderful liberal institutions can be quietly eroded by the forces of darkness, once those forces have sufficient control of the media to hide what they are doing. The 'rule of law' is wobbling. |
| 23141 | Left-wingers are inconsistent in their essentialist descriptions of social groups [Gopnik] |
| Full Idea: A criticism of the left is that it is essentialist at some moments, and wildly anti-essentialist at others. We can call this opportunistic essentialism. Gender is fluid - except for transgender kids. Race is a construction - except for white races. | |
| From: Adam Gopnik (A Thousand Small Sanities [2019], 3) | |
| A reaction: [compressed] Interesting. Gopnik's solution seems to be to abandon all social essentialism as wicked. In this context he is probably right, but I am firmly committed to the idea that many entities in the world have essential natures. 'Bourgeois'. |
| 23124 | Liberal community is not blood ties or tradition, but shared choices, and sympathy for the losers [Gopnik] |
| Full Idea: The liberal idea of community is not one, as it is for many conservatives, of blood ties or traditional authority. It rest on the idea of shared choices …including even a sense of sympathy for those caught on the losing side of the argument. | |
| From: Adam Gopnik (A Thousand Small Sanities [2019], 1) | |
| A reaction: The key point is that most liberals (other than extreme libertarians) have a strong sense of community, contrary to the standard criticisms offered by communitarians. |
| 23127 | Liberal community includes flight from the family, into energetic reforming groups [Gopnik] |
| Full Idea: Where conservatives believe in the renewal of traditional community, liberals believe as well in the flight from family and tradition into new kinds of communal order. …It is an idea of assembling confidence and energies for reform. | |
| From: Adam Gopnik (A Thousand Small Sanities [2019], 1) | |
| A reaction: He cites Greenwich Village as an example. This suggests that his vision is a little narrow. His communities are for radicals who flee to join like minds in big cities. Politics must care about community for those left behind. Pubs, sport and pets. |
| 23129 | Right-wingers attack liberal faith in reason, left-wingers attack its faith in reform [Gopnik] |
| Full Idea: The right-wing critique of liberalism is largely an attack on its overreliance on reason; the left-wing one, mostly an attack on its false faith in reform. | |
| From: Adam Gopnik (A Thousand Small Sanities [2019], 2) | |
| A reaction: I doubt whether sensible liberals do rely too much on reason, though they do rely of scientific evidence (after peer review!). No one can doubt that lots of reforms have occurred, so it must be frustration with the very slow process. |
| 23133 | Cosmopolitan liberals lack national loyalty, and welcome excessive immigration [Gopnik] |
| Full Idea: Critics say liberal cosmopolitanism is indifference to national loyalty, making them easily contemplate going elsewhere and, worse still, welcoming in the world through unsifted immigration. | |
| From: Adam Gopnik (A Thousand Small Sanities [2019], 2) | |
| A reaction: There is certainly some truth in this. Not all liberals are so cosmopolitan, though. It is interesting to observe whether people who retire stay in their old community or move to somewhere quite new. |
| 23138 | Modern left-wingers criticise liberalism's control of culture [Gopnik] |
| Full Idea: Most left-wing critiques of liberalism now turn more often on its cultural power and its cultural illusions. | |
| From: Adam Gopnik (A Thousand Small Sanities [2019], 3) | |
| A reaction: As opposed to older Marxists critiques of the exploitation of workers. This is certainly fertile ground for interesting studies of our culture. It is very hard to grasp the influence had by the endless stories we expose ourselves to. |
| 23139 | Liberalism's attempt to be neutral and colour-blind erases cultural identities [Gopnik] |
| Full Idea: The 'colour-blind' universe of 'neutral' liberalism is actually an attempt to erase cultural identity and history. | |
| From: Adam Gopnik (A Thousand Small Sanities [2019], 3) | |
| A reaction: This is the modern critique of liberalism [centred on the Intersectionality of Bell Hooks or Kimberlé Crenshaw], which analyses alienated minorities, and their emphasis on their difference in response. It can lead to 'identity politics'. |
| 23135 | Classic Marxists see liberalism as the ideology of the bourgeoisie [Gopnik] |
| Full Idea: The classic Marxist account shows liberalism as merely the ideology of the bourgeoisie. | |
| From: Adam Gopnik (A Thousand Small Sanities [2019], 3) | |
| A reaction: The word 'merely' does an awful lot of work in philosohy! I suspect that 'bourgeoisie' is self-defining here - as the believers in liberalism - given that lots of Marxists emerge from the middle classes. |
| 23140 | Environmental disasters result not from capitalism, but from a general drive for growth [Gopnik] |
| Full Idea: It is the drive for growth, not capitalism in particular, that makes environmental disasters happen. Those caused by the command economics of Eastern Europe were far greater than even the worst known in Western Europe. | |
| From: Adam Gopnik (A Thousand Small Sanities [2019], 3) | |
| A reaction: So the next question is whether you can have capitalism without a drive for growth. I would have thought not, given the role recycled profit plays in driving capitalism. Command economies are more easily swept away. |
| 23130 | Popular imperialism gives the poor the belief that their acts have world historical meaning [Gopnik] |
| Full Idea: Popular imperialism is the cosmopolitanism of the poor, the lever by which the small and impotent come to believe that their acts have world historical meaning. | |
| From: Adam Gopnik (A Thousand Small Sanities [2019], 2) | |
| A reaction: It is not only the poor who like imperialism. The focus of this popular attitude is the armed forces, and especially the army, where personal bravery is most obvious. The army gets strong support, no matter how dubious are its activities. |
| 23131 | Patriots love their place, but nationalists have a paranoid ethnic hostility [Gopnik] |
| Full Idea: The patriot loves his place and its cheeses; …the nationalist has not particular affection for the place, but employs his obsessive sense of encirclement and grievance on behalf of acts of ethnic vengeance. | |
| From: Adam Gopnik (A Thousand Small Sanities [2019], 2) | |
| A reaction: 'Vengeance' seems a bit strong. John Le Carré said nationalists are distinguished by the need to have enemies. Russia is particularly obsessed with 'encirclement'. |
| 23136 | Liberal free speech is actually paid speech [Gopnik] |
| Full Idea: What liberals call free speech or a free press is invariably paid speech. | |
| From: Adam Gopnik (A Thousand Small Sanities [2019], 3) | |
| A reaction: He give this as the left-wing view of liberalism. The much-hated social media are a substantial breech in this tendency. Sales of newspapers are declining everywhere, so the battle is for television channels. |
| 23134 | A 'free' society implies a free market, which always produces predatory capitalism and inequalities [Gopnik] |
| Full Idea: 'Free societies', as a matter of practical fact, always mean free-market societies - and free markets will never sponsor more than predatory capitalism. Inequalities always emerge. | |
| From: Adam Gopnik (A Thousand Small Sanities [2019], 3) | |
| A reaction: This is part of his account of left-wing objections to liberalism. The crux of the liberal view is a conviction that the worst of capitalism can be restrained. This began to look doubtful once huge multinational companies emerged. What to do? |
| 5833 | Education is the greatest of human goods [Xenophon] |
| Full Idea: Education is the greatest of human goods. | |
| From: Xenophon (Apology of Socrates [c.392 BCE], 22) | |
| A reaction: Of course, one might ask what education is for, and arrive at a greater good. If you ask what is the greatest good which a society can provide for you, or which you can give to your children, this seems to me a good answer. |