37 ideas
13838 | A decent modern definition should always imply a semantics [Hacking] |
Full Idea: Today we expect that anything worth calling a definition should imply a semantics. | |
From: Ian Hacking (What is Logic? [1979], §10) | |
A reaction: He compares this with Gentzen 1935, who was attempting purely syntactic definitions of the logical connectives. |
13833 | 'Thinning' ('dilution') is the key difference between deduction (which allows it) and induction [Hacking] |
Full Idea: 'Dilution' (or 'Thinning') provides an essential contrast between deductive and inductive reasoning; for the introduction of new premises may spoil an inductive inference. | |
From: Ian Hacking (What is Logic? [1979], §06.2) | |
A reaction: That is, inductive logic (if there is such a thing) is clearly non-monotonic, whereas classical inductive logic is monotonic. |
13834 | Gentzen's Cut Rule (or transitivity of deduction) is 'If A |- B and B |- C, then A |- C' [Hacking] |
Full Idea: If A |- B and B |- C, then A |- C. This generalises to: If Γ|-A,Θ and Γ,A |- Θ, then Γ |- Θ. Gentzen called this 'cut'. It is the transitivity of a deduction. | |
From: Ian Hacking (What is Logic? [1979], §06.3) | |
A reaction: I read the generalisation as 'If A can be either a premise or a conclusion, you can bypass it'. The first version is just transitivity (which by-passes the middle step). |
13835 | Only Cut reduces complexity, so logic is constructive without it, and it can be dispensed with [Hacking] |
Full Idea: Only the cut rule can have a conclusion that is less complex than its premises. Hence when cut is not used, a derivation is quite literally constructive, building up from components. Any theorem obtained by cut can be obtained without it. | |
From: Ian Hacking (What is Logic? [1979], §08) |
13845 | The various logics are abstractions made from terms like 'if...then' in English [Hacking] |
Full Idea: I don't believe English is by nature classical or intuitionistic etc. These are abstractions made by logicians. Logicians attend to numerous different objects that might be served by 'If...then', like material conditional, strict or relevant implication. | |
From: Ian Hacking (What is Logic? [1979], §15) | |
A reaction: The idea that they are 'abstractions' is close to my heart. Abstractions from what? Surely 'if...then' has a standard character when employed in normal conversation? |
13840 | First-order logic is the strongest complete compact theory with Löwenheim-Skolem [Hacking] |
Full Idea: First-order logic is the strongest complete compact theory with a Löwenheim-Skolem theorem. | |
From: Ian Hacking (What is Logic? [1979], §13) |
13844 | A limitation of first-order logic is that it cannot handle branching quantifiers [Hacking] |
Full Idea: Henkin proved that there is no first-order treatment of branching quantifiers, which do not seem to involve any idea that is fundamentally different from ordinary quantification. | |
From: Ian Hacking (What is Logic? [1979], §13) | |
A reaction: See Hacking for an example of branching quantifiers. Hacking is impressed by this as a real limitation of the first-order logic which he generally favours. |
13842 | Second-order completeness seems to need intensional entities and possible worlds [Hacking] |
Full Idea: Second-order logic has no chance of a completeness theorem unless one ventures into intensional entities and possible worlds. | |
From: Ian Hacking (What is Logic? [1979], §13) |
13837 | With a pure notion of truth and consequence, the meanings of connectives are fixed syntactically [Hacking] |
Full Idea: My doctrine is that the peculiarity of the logical constants resides precisely in that given a certain pure notion of truth and consequence, all the desirable semantic properties of the constants are determined by their syntactic properties. | |
From: Ian Hacking (What is Logic? [1979], §09) | |
A reaction: He opposes this to Peacocke 1976, who claims that the logical connectives are essentially semantic in character, concerned with the preservation of truth. |
13839 | Perhaps variables could be dispensed with, by arrows joining places in the scope of quantifiers [Hacking] |
Full Idea: For some purposes the variables of first-order logic can be regarded as prepositions and place-holders that could in principle be dispensed with, say by a system of arrows indicating what places fall in the scope of which quantifier. | |
From: Ian Hacking (What is Logic? [1979], §11) | |
A reaction: I tend to think of variables as either pronouns, or as definite descriptions, or as temporary names, but not as prepositions. Must address this new idea... |
13843 | If it is a logic, the Löwenheim-Skolem theorem holds for it [Hacking] |
Full Idea: A Löwenheim-Skolem theorem holds for anything which, on my delineation, is a logic. | |
From: Ian Hacking (What is Logic? [1979], §13) | |
A reaction: I take this to be an unusually conservative view. Shapiro is the chap who can give you an alternative view of these things, or Boolos. |
6019 | If someone squashed a horse to make a dog, something new would now exist [Mnesarchus] |
Full Idea: If, for the sake of argument, someone were to mould a horse, squash it, then make a dog, it would be reasonable for us on seeing this to say that this previously did not exist but now does exist. | |
From: Mnesarchus (fragments/reports [c.120 BCE]), quoted by John Stobaeus - Anthology 179.11 | |
A reaction: Locke would say it is new, because the substance is the same, but a new life now exists. A sword could cease to exist and become a new ploughshare, I would think. Apply this to the Ship of Theseus. Is form more important than substance? |
7222 | It is a crime for someone with a violent disposition to get drunk [Mill] |
Full Idea: The making himself drunk, in a person whom drunkenness excites to do harm to others, is a crime against others. | |
From: John Stuart Mill (On Liberty [1857], Ch.5) | |
A reaction: This principle (based on knowing your own dispositions) is a very good account of the ethics drunkenness. We have a moral duty to know and remember our own dispositions. Violent people should avoid arguments as well as alcohol. |
7214 | Ethics rests on utility, which is the permanent progressive interests of people [Mill] |
Full Idea: I regard utility as the ultimate appeal on all ethical questions; but it must be utility in the largest sense, grounded on the permanent interests of a man as a progressive being. | |
From: John Stuart Mill (On Liberty [1857], Ch.1) | |
A reaction: Mill, writing in praise of personal liberty, is desperate to introduce a paternalistic element into his politics, and the 'maximisation of happiness' will justify such paternalism, while his basic liberal principle (Idea 7211) won't. Mill's Dilemma. |
7212 | Individuals have sovereignty over their own bodies and minds [Mill] |
Full Idea: Over himself, over his own body and mind, the individual is sovereign. | |
From: John Stuart Mill (On Liberty [1857], Ch.1) | |
A reaction: If I should not even think about evil deeds, then neither should you. I would prevent you if I could. I would prevent you from drinking yourself to death, if I could. It is just that intrusions into private lives leads to greater trouble. |
7210 | The will of the people is that of the largest or most active part of the people [Mill] |
Full Idea: The will of the people practically means the will of the most numerous or the most active part of the people. | |
From: John Stuart Mill (On Liberty [1857], Ch.1) | |
A reaction: Hence the nicely coined modern phrase 'the silent majority', on whose behalf certain politicians, usually conservative, offer to speak. It is unlikely that the silent majority are actually deeply opposed to the views of the very active part. |
7227 | It is evil to give a government any more power than is necessary [Mill] |
Full Idea: Government interference should be restricted because of the great evil of adding unnecessarily to its power. | |
From: John Stuart Mill (On Liberty [1857], Ch.5) | |
A reaction: This would need justification, because it might be replied that individuals should not have unnecessary power either. The main problem is that governments have armies, police and money. |
7228 | Individuals often do things better than governments [Mill] |
Full Idea: Government power should be restricted because things are often done better by individuals. | |
From: John Stuart Mill (On Liberty [1857], Ch.5) | |
A reaction: This contains some truth, but it is obvious that innumerable things can be done better by governments, and also (and more importantly) that innumerable other good things might be done by governments which individuals can't be bothered to do. |
7230 | Aim for the maximum dissemination of power consistent with efficiency [Mill] |
Full Idea: The safest practical ideal is to aim for the greatest dissemination of power consistent with efficiency. | |
From: John Stuart Mill (On Liberty [1857], Ch.5) | |
A reaction: This is a very nice principle, which I would think desirable within an institution as well as on the scale of the state. I am becoming a fan of Mill's politics. I still say that freedom is an overrated virtue, so efficiency must be underrated. |
20515 | Maximise happiness by an area of strict privacy, and an area of utilitarian interventions [Mill, by Wolff,J] |
Full Idea: For Mill the greatest happiness will be achieved by giving people a private sphere of interests where no intervention is permitted, while allowing a public sphere where intervention is possible, but only on utilitarian grounds. | |
From: report of John Stuart Mill (On Liberty [1857]) by Jonathan Wolff - An Introduction to Political Philosophy (Rev) 4 'Liberty' | |
A reaction: This is probably standard liberal practice nowadays. Freely consenting adult sexual activity is agreed to be wholly private. At least some lip-service is paid to increasing happiness when government intervenes. |
7229 | People who transact their own business will also have the initiative to control their government [Mill] |
Full Idea: A people accustomed to transacting their own business is certain to be free; it will never let itself be enslaved by any man or body of men because these are able to seize and pull the reins of the central administration. | |
From: John Stuart Mill (On Liberty [1857], Ch.5) | |
A reaction: He makes reference to Americans. This is an important idea, because it shows that democratic control is not just a matter of elections (which can be abolished or suborned), but is also a characteristic of a certain way of life. |
7211 | Prevention of harm to others is the only justification for exercising power over people [Mill] |
Full Idea: The only purpose for which power can be rightfully exercised over any member of a civilised community, against his will, is to prevent harm to others; his own good, either physical or moral, is not a sufficient warrant. | |
From: John Stuart Mill (On Liberty [1857], Ch.1) | |
A reaction: This is the key idea in Mill's liberalism, though he goes on to offer some qualifications of this absolute prohibition. I don't disagree with this principle, but there may be a lot more indirect harm than we realise (eg. in allowing liberal sex or drugs). |
7231 | The worth of a State, in the long run, is the worth of the individuals composing it [Mill] |
Full Idea: The worth of a State, in the long run, is the worth of the individuals composing it. | |
From: John Stuart Mill (On Liberty [1857], Ch.5) | |
A reaction: This is a key idea of liberalism, opposed to any idea that we should abandon our own value to that of our state. I agree, but communitarians can subscribe to this too, while disagreeing that maximum freedom is the strategy to follow. |
7217 | The main argument for freedom is that interference with it is usually misguided [Mill] |
Full Idea: The strongest of all the arguments against the interference of the public with purely personal conduct is that, when it does interfere, the odds are that it interferes wrongly, and in the wrong place. | |
From: John Stuart Mill (On Liberty [1857], Ch.4) | |
A reaction: This is also a well known objection to capital punishment. Generalised, well established, legal interferences are perhaps more likely to get it right than ad hoc decisions about individuals by individual officials. |
7213 | Liberty arises at the point where people can freely and equally discuss things [Mill] |
Full Idea: Liberty, as a principle, has no application to any state of things anterior to the time when mankind have become capable of being improved by free and equal discussion. | |
From: John Stuart Mill (On Liberty [1857], Ch.1) | |
A reaction: There is a Victorian (and Enlightenment) optimism here which a glimpse of the freedoms of the early twenty-first century might dampen. I doubt if Mill expected British tabloid newspapers, or porn on cable TV. Education and freedom connect. |
7221 | Blocking entry to an unsafe bridge does not infringe liberty, since no one wants unsafe bridges [Mill] |
Full Idea: An official could turn a person back from an unsafe bridge without infringeing their liberty; for liberty consists in doing what one desires, and he does not desire to fall into the river. | |
From: John Stuart Mill (On Liberty [1857], Ch.5) | |
A reaction: Seems fair enough, but it justifies paternalist interference. The tricky one is where the official and the citizen disagree over what the citizen 'truly' desires. Asking people may involve too much time, but it could also involve too much effort. |
7223 | Pimping and running a gambling-house are on the border between toleration and restraint [Mill] |
Full Idea: A person being free to be a pimp, or to keep a gambling-house, lies on the exact boundary line between two principles, of toleration and of restraint. | |
From: John Stuart Mill (On Liberty [1857], Ch.5) | |
A reaction: Nothing illuminates a philosopher's principles more than for them to specify cases that lie on their borderlines. Both professions seem, unfortunately, to lead people into worse activities, such as violent bullying, or theft. Tricky.. |
7220 | Restraint for its own sake is an evil [Mill] |
Full Idea: All restraint, qua restraint, is an evil. | |
From: John Stuart Mill (On Liberty [1857], Ch.5) | |
A reaction: The ultimate justification for this is (presumably) utilitarian, but that would mean that there was nothing wrong with restraint if the person did not mind, or was not aware of the restraint. What is intrinsically wrong with restraint? |
20516 | Mill defends freedom as increasing happiness, but maybe it is an intrinsic good [Wolff,J on Mill] |
Full Idea: Mill has presented liberty as instrumentally valuable, as a way of achieving the greatest possible happiness in society. But perhaps he should have argued that liberty is an intrinsic good, good in itself. | |
From: comment on John Stuart Mill (On Liberty [1857]) by Jonathan Wolff - An Introduction to Political Philosophy (Rev) 4 'Intrinsic' | |
A reaction: If freedom is intrinsically good, does this leave us (as Wolff warned earlier) unable to defend its value? Freedom isn't an intrinsic good for infants, so why should it be so for adults? Good because it brings happiness, or fulfils our nature? |
7215 | True freedom is pursuing our own good, while not impeding others [Mill] |
Full Idea: The only freedom which deserves the name, is that of pursuing our own good in our own way, so long as we do not attempt to deprive others of theirs, or impede their efforts to obtain it. | |
From: John Stuart Mill (On Liberty [1857], Ch.1) | |
A reaction: This principle will probably lead up a Prisoner's Dilemma cul-de-sac. The only freedom which deserves the name is the collective agreed freedom of a whole community to live well, when citizens volunteer to restrict their individual freedoms. |
7218 | Individuals are not accountable for actions which only concern themselves [Mill] |
Full Idea: My first maxim is that the individual is not accountable to society for his actions, in so far as these concern the interests of no person but himself. | |
From: John Stuart Mill (On Liberty [1857], Ch.5) | |
A reaction: This is a key idea of liberalism, and one which communitarians have doubts about (because it is almost impossible to perform an action which is of no interest, in the short or long term, to others). I share these doubts. |
20517 | Utilitarianism values liberty, but guides us on which ones we should have or not have [Mill, by Wolff,J] |
Full Idea: Utilitarianism provides an account of what liberties we should and should not have. Mill argues we should be free to compete in trade, but not to use another's property without consent. Thus he sets limits to liberty, while paying it great respect. | |
From: report of John Stuart Mill (On Liberty [1857]) by Jonathan Wolff - An Introduction to Political Philosophy (Rev) 4 'Intrinsic' |
7219 | Society can punish actions which it believes to be prejudicial to others [Mill] |
Full Idea: My second maxim is that for actions that are prejudicial to the interests of others, the individual is accountable, and subject to social or legal punishment, if society believes that this is requisite for its protection. | |
From: John Stuart Mill (On Liberty [1857], Ch.5) | |
A reaction: (wording compressed). The trouble with this would seem to be the possible disagreement between the individual and the society over whether the actions actually are prejudicial to others. It would justify a conservative society in being repressive. |
7226 | Benefits performed by individuals, not by government, help also to educate them [Mill] |
Full Idea: It is often desirable that beneficial things should be done by individuals, rather than by the government, as a means to their own mental education. | |
From: John Stuart Mill (On Liberty [1857], Ch.5) | |
A reaction: This raises the important danger, which even those on the political left must acknowledge, of the 'nanny state'. It offers a nicely paternalistic, and even patronising reason for giving people freedom, just as a parent might to a child. |
7224 | We need individual opinions and conduct, and State education is a means to prevent that [Mill] |
Full Idea: Individuality of character, and diversity in opinions and modes of conduct, involves diversity of education; a general State education is a mere contrivance for moulding people to be exactly like one another. | |
From: John Stuart Mill (On Liberty [1857], Ch.5) | |
A reaction: This strikes me as being particularly true with the advent in Britain of the National Curriculum in the early 1990s. However, if there is a pressure towards conformity in state education, private education is dominated by class and money. |
7225 | It is a crime to create a being who lacks the ordinary chances of a desirable existence [Mill] |
Full Idea: To bestow a life on someone which may be either a curse or a blessing, unless the being on whom it is to be bestowed will have at least the ordinary chances of a desirable existence, is a crime against that being. | |
From: John Stuart Mill (On Liberty [1857], Ch.5) | |
A reaction: This is the standard utilitarian attitude to engendering people. I think I have to agree. It is no argument against this to say that we value people with poor life prospects, once they have arrived. Altruism towards children may disguise selfish parents. |
7216 | The ethics of the Gospel has been supplemented by barbarous Old Testament values [Mill] |
Full Idea: To extract from the Gospel a body of ethical doctrine, has never been possible withouth eking it out from the Old Testament, that is, from a system elaborate indeed, but in many respects barbarous, and intended only for a barbarous people. | |
From: John Stuart Mill (On Liberty [1857], Ch.2) | |
A reaction: 'Barbarous' has a quaint Victorian ring to it, but his point is that the surviving teachings of Jesus are very thin and generalised. Christians would do better to expand their implications, than to borrow from the Old Testament. |