39 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. |
| 541 | Virtue comes more from habit than character [Critias] |
| Full Idea: More men are good through habit than through character. | |
| From: Critias (fragments/reports [c.440 BCE], B09), quoted by John Stobaeus - Anthology 3.29.41 |
| 20547 | We should respect the right of people to live in their own way, even if it is irrational [Swift] |
| Full Idea: Forcing people to do what is rational involves a lack of respect, a failure to respect the value of her living her life in her own (irrational) way. | |
| From: Adam Swift (Political Philosophy (3rd ed) [2014], 2 'Resisting' 6) | |
| A reaction: Up to a point. Irrationally eccentric is one thing, and irrationally self-destructive is another. You can sit back and watch your children embrace a life less happy than the one you wanted for them - but not a life of utter misery. |
| 20564 | Anti-colonial movements usually invoke the right of their 'people' to self-determination [Swift] |
| Full Idea: Nationalist movements seeking to throw off the yoke of colonial rule are often motivated by a sense that their 'people' have the right to self-determination. | |
| From: Adam Swift (Political Philosophy (3rd ed) [2014], 5 'Intrinsic 1') | |
| A reaction: In 2017, Basques, Catalans and Kurds come to mind. The whole of Africa was an example of this c.1950-80, but there was uncertainty about states, tribes and language groups. |
| 20535 | Isn't it more rational to maximise the average position, but with a safety net? [Swift] |
| Full Idea: Wouldn't it be more rational to choose principles that would maximize the average position, perhaps subject to some 'floor' level beneath which they would not want to take the risk of sinking? | |
| From: Adam Swift (Political Philosophy (3rd ed) [2014], 1 'Rawls') | |
| A reaction: The criticism is that Rawls's prediction is over-cautious, and that people will take mild risks in what they choose, as long as there is no danger of disaster. (Just as you should allow small children to risk injury, but not death). |
| 20537 | Hypothetical contracts have no binding force [Swift] |
| Full Idea: A common objection to Rawls is that hypothetical contracts, unlike real ones, have no binding force. | |
| From: Adam Swift (Political Philosophy (3rd ed) [2014], 1 'Rawls') | |
| A reaction: [I think Dworkin made this point] 'Contract' may be metaphorical. Perhaps it is just an 'initial agreement' or a 'working arrangement', |
| 20542 | Cosmopolitans reject the right of different states to distribute resources in different ways [Swift] |
| Full Idea: Cosmopolitans who claim that the same distributive principles should apply to all human beings seem to be denying that different states may make different judgements about how they want to allocate resources among their members. | |
| From: Adam Swift (Political Philosophy (3rd ed) [2014], 1 'Social') | |
| A reaction: If you want to be a citizen of the world, you have to face up to the pluralistic character of cultures. Do you thereby want to be a citizen of both California and Saudi Arabia? Or are you actually just becoming a citizen of nowhere? |
| 20559 | Democracy is bad, but the other systems are worse [Swift] |
| Full Idea: During WW2 Winston Churchill famously said that democracy is the worst form of government, except for all the others that have been tried. | |
| From: Adam Swift (Political Philosophy (3rd ed) [2014], 5 'Procedures') | |
| A reaction: [Actually a speech in 1947, which began 'it has been said that....'] Aristotle thought an intelligent and benevolent dictatorship was the best form, but held little hope of achieving it. Getting rid of bad rulers is the big virtue. |
| 20561 | Since all opinions are treated as equal in democracy, it implies there are no right answers [Swift] |
| Full Idea: If there were moral knowledge about political matters, democracy would be a very strange way of reaching it. Democratic law-making means treating each person's view as equally good, which only makes sense if there is nothing to be right or wrong about. | |
| From: Adam Swift (Political Philosophy (3rd ed) [2014], 5 'Subjectivism') | |
| A reaction: Ah, I suddenly grasp that the modern fad for a rather gormless blanket relativism is rooted in the modern desire to take democracy really seriously. Important to remember Condorcet's point here. |
| 20562 | Design your democracy to treat citizens equally, or to produce better citizens? [Swift] |
| Full Idea: If your main reason for being a democrat is that democratic procedures respect citizens equally, then you may want a different kind of democracy from those who favour it because they think it tends to produce better citizens? | |
| From: Adam Swift (Political Philosophy (3rd ed) [2014], 5 'Values') | |
| A reaction: [Combine this with Idea 20563] |
| 20563 | Design your democracy to yield political stability, or good decisions? [Swift] |
| Full Idea: If you value democracy because it yields political stability, then you will probably worry about different aspects of the procedure from those who care about its producing good decisions. | |
| From: Adam Swift (Political Philosophy (3rd ed) [2014], 5 'Values') | |
| A reaction: [Combine this with Idea 20562] Surely the primary aim must be good decisions? The other three options are the result of pessimism about any method achieving that. Instability, inequality and dud citizens are bars to good decisions. |
| 20560 | Teledemocracy omits debate and deliberation, which are important parts of good decisions [Swift] |
| Full Idea: We are averse to teledemocracy because it misses out some important parts of a good decision-making procedure, such as debate and deliberation. | |
| From: Adam Swift (Political Philosophy (3rd ed) [2014], 5 'Procedures') | |
| A reaction: Perhaps you should be sent a short info pack, and only allowed to vote when you have passed a factual multiple choice test about the topic. Or one pack from each political party. Maybe compulsory online discussion as well. |
| 20554 | Multiculturalism is a barrier to the whole state being a community [Swift] |
| Full Idea: For those wanting to regard the state itself as a community, multiculturalism can be a problem. | |
| From: Adam Swift (Political Philosophy (3rd ed) [2014], 4 'Liberalism') | |
| A reaction: A very important idea. A certain type of aggressive patriot passionately wants the whole country to be a close-bound community, and becomes deeply frustrated by the impossibility of this in a complex and fluid modern world. |
| 20553 | Liberals mistakenly think individuals choose their values, without reference to the community [Swift] |
| Full Idea: The two core liberal mistakes (according to communitarians) are that people choose their values, and that they do so in some way detached from their communities. | |
| From: Adam Swift (Political Philosophy (3rd ed) [2014], 4 'Correcting') | |
| A reaction: I think I might be a communitarian liberal, meaning that extreme individualism is both incorrect and pernicious, but that communities should only exist to promote the varied lives of individuals within them. |
| 20556 | The best way to build a cohesive community is to be involved in a war [Swift] |
| Full Idea: There is nothing like a war to build a sense of common purpose, of being in the same boat, and to generate the kind of interaction between people that breaks down divisive social boundaries. | |
| From: Adam Swift (Political Philosophy (3rd ed) [2014]) | |
| A reaction: A nice warning to those who over-do or simplify communitarianism. Alternatively, the greatest sign of health in a community is that citizens have almost no interest in one another? |
| 20557 | Membership and inclusion in a community implies non-membership and exclusion [Swift] |
| Full Idea: Community is about membership and inclusion. But that means it is also about non-membership and exclusion. | |
| From: Adam Swift (Political Philosophy (3rd ed) [2014], 4 'Conc') | |
| A reaction: I'm a fan of communitarianism (focused on Aristotle's life of individual virtue for each citizen), but I'm beginning to see that it has a poisonous cousin travelling under the same name. The cousin's rallying cries focus on aliens and enemies. |
| 20555 | Liberals are concerned to protect individuals from too much community [Swift] |
| Full Idea: Liberals are concerned to protect individuals from too much community - from practices that stifle the individual's freedom to choose for herself how she lives her life. | |
| From: Adam Swift (Political Philosophy (3rd ed) [2014], 4 'Liberalism') | |
| A reaction: The phrase 'too much community' is an excellent warning to communitarians. I'm happy to be enmeshed in a community, as long as it is composed of highly liberal and easy-going individuals. Avoid too much bad community. |
| 20540 | Redistributing wealth treats some people as means, rather than as ends [Swift] |
| Full Idea: Treating people as means seems like a fairly accurate description of what is involved when the state coercively redistributes resources from some to others. | |
| From: Adam Swift (Political Philosophy (3rd ed) [2014], 1 'Nozick') | |
| A reaction: The objection comes from Nozick, and alludes to Kant's desire to treat everyone as an end in themselves. Personally I don't mind at all being treated as a means, when my wife asks me to make her a cup of tea. Or paying my taxes to help the community. |
| 20551 | Men have had the power to structure all of our social institutions [Swift] |
| Full Idea: The problem for feminists is that men have had the power to structure all our social institutions - family, economy, polity - in ways that suit them. | |
| From: Adam Swift (Political Philosophy (3rd ed) [2014], 3 'Gender') | |
| A reaction: An interesting question is whether masculine domination runs even deeper than that, into our value system, our metaphysics, our science, our epistemology, our language. How do you tell? If women take over half the masculine roles, does that solve it? |
| 20545 | Maybe a freedom is from a restraint, and also in order to do something [Swift] |
| Full Idea: Maybe freedom is a triadic relation, involving an agent, freedom from a contraint, and in order to act towards some goal. | |
| From: Adam Swift (Political Philosophy (3rd ed) [2014], 2 'Two') | |
| A reaction: [He cites Gerald MacCallum for this thought] The point is that this makes freedom both negative and positive, contrary to Isaiah Berlin's claim. But on the first day of the school holidays you are 'free', with nothing in particular in mind. |
| 20550 | Opportunity should ignore extraneous factors, or foster competence, or ignore all disadvantages [Swift] |
| Full Idea: The minimal conception of equality of opportunity is that race or gender or religion should not affect chances of a good job or education. The conventional conception needs equality in acquiring competences. Radical views ignore inborn disadvantages. | |
| From: Adam Swift (Political Philosophy (3rd ed) [2014], 3 'Equality') | |
| A reaction: [my summary of Swift] The strong version only says the less talented should have access to large rewards. The whole idea has strong capitalist assumptions. |
| 20536 | Inequalities are needed, as incentives to do the most important jobs [Swift] |
| Full Idea: Without inequalities, people will have no incentive to do one job rather than another - to do the kind of work which is most useful. | |
| From: Adam Swift (Political Philosophy (3rd ed) [2014], 1 'Rawls') | |
| A reaction: The reality is that the lowest pay goes to the jobs that no one wants to do, and all the really nice jobs are usually well paid. Which is a conspiracy, because all the salaries are set by the people with the nice jobs. |
| 20548 | A person can desire redistibution of wealth, without it being for reasons of equality [Swift] |
| Full Idea: Someone who rejects equality can care passionately that resources should be transferred from the rich to the poor. They are just rejecting a particular reason that might be offered to justify the redistribution. | |
| From: Adam Swift (Political Philosophy (3rd ed) [2014], 3 'Intro') | |
| A reaction: For example, it might be for utilitarian reasons, which usually only seek maximised happiness, not equal happiness. And one may love many forms of equality, without economic equality being one of them. |
| 20541 | You can't necessarily sell your legitimate right to something, even if you produced it [Swift] |
| Full Idea: Ownership is a complicated idea. I have a right to the office photocopier, but I can's sell the right to others. If people have absolute rights over what they produce, why can't parents sell their children into slavery? | |
| From: Adam Swift (Political Philosophy (3rd ed) [2014], 1 'Nozick') | |
| A reaction: If I make a car from stolen parts, does constructing it make it mine? Etc. Do birds own their nests? Swift goes on to ask if we 'own' our bodies. |
| 20546 | Libertarians about property ignore the fact that private property is a denial of freedoms [Swift] |
| Full Idea: Libertarians say that they care about freedom, and argue for private property rights on freedom grounds. But they don't sem to care about, or even notice, the unfreedom implied by the existence of private property rights. | |
| From: Adam Swift (Political Philosophy (3rd ed) [2014], 2 'Freedom') | |
| A reaction: When I pass some vast country estate totally surrounded by a high wall, I certainly don't think how wonderful it is that someone has the right to own this property as private land. On the contrary.... |
| 20533 | Justice can be seen as fairness or entitlement or desert [Swift] |
| Full Idea: The three influential conceptions of justice are as fairness (Rawls), as entitlement (Nozick), and as desert. | |
| From: Adam Swift (Political Philosophy (3rd ed) [2014], 1 'Concept') |
| 542 | Fear of the gods was invented to discourage secret sin [Critias] |
| Full Idea: When the laws forbade men to commit open crimes of violence, and they began to do them in secret, a wise and clever man invented fear of the gods for mortals, to frighten the wicked, even if they sin in secret. | |
| From: Critias (fragments/reports [c.440 BCE], B25), quoted by Sextus Empiricus - Against the Professors (six books) 9.54 |