38 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. |
| 2584 | Lobotomised patients can cease to care about a pain [Block] |
| Full Idea: After frontal lobotomies, patients typically report that they still have pains, though the pains no longer bother them. | |
| From: Ned Block (Troubles with Functionalism [1978], p. 83) | |
| A reaction: I take this to be an endorsement of reductive physicalism, because what matters about pains is that they bother us, not how they feel, so frog pain could do the job, if it felt different from ours, but was disliked by the frog. |
| 6172 | The Inverted Earth example shows that phenomenal properties are not representational [Block, by Rowlands] |
| Full Idea: Block's Inverted Earth example (with matching inversion of both colours and colour-language) tries to show a variation of representational properties without a variation of phenomenal properties, so that the latter are not constituted by the former. | |
| From: report of Ned Block (Inverted Earth [1990]) by Mark Rowlands - Externalism Ch.7 | |
| A reaction: (The example is actually quite complex). This type of argument - a thought experiment in which qualia are held steady while everything else varies, or vice versa - seems to be the only way that we can possibly get at an assessment of the role of qualia. |
| 2582 | A brain looks no more likely than anything else to cause qualia [Block] |
| Full Idea: NO physical mechanism seems very intuitively plausible as a seat of qualia, least of all a brain. | |
| From: Ned Block (Troubles with Functionalism [1978], p. 78) | |
| A reaction: I'm not sure about "least of all", given the mind-boggling complexity of the brain's connections. Certainly, though, nothing in either folk physics or academic physics suggests that any physical object is likely to be aware of anything. |
| 2574 | Behaviour requires knowledge as well as dispositions [Block] |
| Full Idea: A desire cannot be identified with a disposition to act, since the agent might not know that a particular act leads to the thing desired, and thus might not be disposed to do it. | |
| From: Ned Block (Troubles with Functionalism [1978], p. 69) | |
| A reaction: One might have a disposition to act, but not in a particular way. "Something must be done". To get to the particular act, it seems that indeed a belief must be added to the desire. |
| 2576 | In functionalism, desires are internal states with causal relations [Block] |
| Full Idea: According to functionalism, a system might have the behaviouristic input-output relations, yet not desire something, as this requires internal states with certain causal relations. | |
| From: Ned Block (Troubles with Functionalism [1978], p. 69) | |
| A reaction: Such a system might be Putnam's 'superactor', who only behaves as if he desires something. Of course, the internal states might need more than just 'causal relations'. |
| 2575 | Functionalism is behaviourism, but with mental states as intermediaries [Block] |
| Full Idea: Functionalism is a new incarnation of behaviourism, replacing sensory inputs with sensory inputs plus mental states, and replacing dispositions to act with dispositions plus certain mental states. | |
| From: Ned Block (Troubles with Functionalism [1978], p. 69) | |
| A reaction: I think of functionalism as behaviourism which extends inside the 'black box' between stimulus and response. It proposes internal stimuli and responses. Consequently functionalism inherits some behaviourist problems. |
| 2583 | You might invert colours, but you can't invert beliefs [Block] |
| Full Idea: It is hard to see how to make sense of the analog of color spectrum inversion with respect to non-qualitative states such a beliefs (where they are functionally equivalent but have different beliefs). | |
| From: Ned Block (Troubles with Functionalism [1978], p. 81) | |
| A reaction: I would suggest that beliefs can be 'inverted', because there are all sorts of ways to implement a belief, but colour can't be inverted, because that depends on a particular brain state. It makes good sense to me... |
| 2578 | Could a creature without a brain be in the right functional state for pain? [Block] |
| Full Idea: If pain is a functional state, it cannot be a brain state, because creatures without brains could realise the same Turing machine as creatures with brains. | |
| From: Ned Block (Troubles with Functionalism [1978], p. 70) | |
| A reaction: This strikes me as being a poorly grounded claim. There may be some hypothetical world where brainless creatures implement all our functions, but from here brains look the only plausible option. |
| 2585 | Not just any old functional network will have mental states [Block] |
| Full Idea: If there are any fixed points in the mind-body problem, one of them is that the economy of Bolivia could not have mental states, no matter how it is distorted. | |
| From: Ned Block (Troubles with Functionalism [1978], p. 86) | |
| A reaction: It is hard to disagree with this, but then it can hardly be a serious suggestion that anyone could see how to reconfigure an economy so that it mapped the functional state of the human brain. This is not a crucial problem. |
| 2586 | In functionalism, what are the special inputs and outputs of conscious creatures? [Block] |
| Full Idea: In functionalism, it is very hard to see how there could be a single physical characterization of the inputs and outputs of all and only creatures with mentality. | |
| From: Ned Block (Troubles with Functionalism [1978], p. 87) | |
| A reaction: It would be theoretically possible if the only way to achieve mentality was to have a particular pattern of inputs and outputs. I don't think, though, that 'mentality' is an all-or-nothing concept. |
| 2579 | Physicalism is prejudiced in favour of our neurology, when other systems might have minds [Block] |
| Full Idea: Physicalism is a chauvinist theory: it withholds mental properties from systems that in fact have them. | |
| From: Ned Block (Troubles with Functionalism [1978], p. 71) | |
| A reaction: This criticism interprets physicalism too rigidly. There may be several ways to implement a state. My own view is that other systems might implement our functions, but they won't experience them in a human way. |
| 2577 | Simple machine-functionalism says mind just is a Turing machine [Block] |
| Full Idea: In the simplest Turing-machine version of functionalism (Putnam 1967), mental states are identified with the total Turing-machine state, involving a machine table and its inputs and outputs. | |
| From: Ned Block (Troubles with Functionalism [1978], p. 70) | |
| A reaction: This obviously invites the question of why mental states would be conscious and phenomenal, given that modern computers are devoid of same, despite being classy Turing machines. |
| 2580 | A Turing machine, given a state and input, specifies an output and the next state [Block] |
| Full Idea: In a Turing machine, given any state and input, the machine table specifies an output and the next state. …To have full power the tape must be infinite in at least one direction, and be movable in both directions. | |
| From: Ned Block (Troubles with Functionalism [1978], p. 71) | |
| A reaction: In retrospect, the proposal that this feeble item should be taken as a model for the glorious complexity and richness of human consciousness doesn't look too plausible. |
| 3178 | A fast machine could pass all behavioural tests with a vast lookup table [Block, by Rey] |
| Full Idea: Ned Block proposes a machine (a 'blockhead') which could pass the Turing Test just by looking up responses in a vast look-up table. | |
| From: report of Ned Block (works [1984]) by Georges Rey - Contemporary Philosophy of Mind 5.3 | |
| A reaction: Once you suspected you were talking to a blockhead, I think you could catch it out in a Turing Test. How can the lookup table keep up to date with immediate experience? Ask it about your new poem. |
| 18033 | The meaning of a representation is its role in thought, perception or decisions [Block] |
| Full Idea: According to conceptual role semantics, the meaning of a representation is the role of that representation in the cognitive life of the agent, for example, in perception, thought and decision-making. | |
| From: Ned Block (Semantics, Conceptual Role [1998]) | |
| A reaction: I never believe theories of this kind, because I always find myself asking 'what is the nature of this representation which enables it to play this role?'. |
| 2581 | Intuition may say that a complex sentence is ungrammatical, but linguistics can show that it is not [Block] |
| Full Idea: Linguistics rejects (on theoretical grounds) the intuition that the sentence "the boy the girl the cat bit scratched died" is ungrammatical. | |
| From: Ned Block (Troubles with Functionalism [1978], p. 78) | |
| A reaction: Once we have disentangled it, we practical speakers have no right to say it is ungrammatical. It isn't only theory. The sentence is just stylistically infelicitous. |
| 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. |
| 7404 | Nations are not obliged to help one-another, but are obliged not to harm one another [Grotius, by Tuck] |
| Full Idea: Grotius explored the implications of the idea that nation-states were under no obligation to help one another, but they were obliged not to harm each other. | |
| From: report of Hugo Grotius (On the Law of War and Peace [1625]) by Richard Tuck - Hobbes Ch.1 | |
| A reaction: This is quite a striking disanalogy between accepted personal morality and political morality. There are signs in recent years of some recognition that other nations should not just sit and watch suffering. |
| 7402 | Everyone has a right of self-preservation, and harming others is usually unjustifiable [Grotius, by Tuck] |
| Full Idea: Grotius said that all men would agree that everyone has a fundamental right to preserve themselves, and that wanton or unnecessary injury to another person is unjustifiable. | |
| From: report of Hugo Grotius (On the Law of War and Peace [1625]) by Richard Tuck - Hobbes Ch.1 | |
| A reaction: Who cares if it is 'justifiable'? Do I have to 'justify' killing a mosquito if it lands on my arm? Grotius is taking a step beyond saying that people should defend themselves, to say that they have a 'right' to - the only truly basic right. |
| 21938 | Democracy needs respect for individuality, but the 'community of friends' implies strict equality [Grotius] |
| Full Idea: There is no democracy without respect for irreducible singularity, but there is no democracy with the 'community of friends' without the calculation of majorities, without identifiable representable subjects, all equal. | |
| From: Hugo Grotius (On the Law of War and Peace [1625]), quoted by Simon Glendinning - Derrida: A Very Short Introduction 7 | |
| A reaction: [source not given] Derrida calls this conflict 'tragic'. The obvious reply is that equality is not an absolute. We can be equal in voting rights while being unequal in height or musical talent. |
| 19845 | A person is free to renounce their state, as long as it is not a moment of crisis [Grotius, by Rousseau] |
| Full Idea: Grotius thinks that each person can renounce his state and leave the country. (n15: provided it is not to evade one's duty the moment the homeland needs us; this would be criminal and punishable; it would not be withdrawal, but desertion) | |
| From: report of Hugo Grotius (On the Law of War and Peace [1625]) by Jean-Jacques Rousseau - The Social Contract (tr Cress) III.18 | |
| A reaction: The obvious example is Britons going to America in 1939, or (more controversially) conscripts going to Canada to avoid fighting in Vietnam. I'm unclear whether the idea in the note is that of Grotius or of Rousseau). Is tax exile OK, then? |
| 22133 | Grotius and Pufendorf based natural law on real (rather than idealised) humanity [Grotius, by Ford,JD] |
| Full Idea: Grotius and Pufendorf transformed the natural law tradition by starting from identifiable traits of human nature rather than ideas about what human beings ought to be. | |
| From: report of Hugo Grotius (On the Law of War and Peace [1625]) by J.D. Ford - Pufendorf, Samuel p.863 |
| 7406 | A natural right of self-preservation is balanced by a natural law to avoid unnecessary harm [Grotius, by Tuck] |
| Full Idea: For Grotius, there was a fundamental 'natural right' of self-preservation upon which all known moralities and codes of social behaviour must have been constructed, but it is balanced by a fundament duty or 'natural law' to abstain from harming others. | |
| From: report of Hugo Grotius (On the Law of War and Peace [1625]) by Richard Tuck - Hobbes Ch.2 | |
| A reaction: This theory has the virtue of economy, but I don't see how you can clearly justify those particular natural rights and laws, without allowing others to creep in, such as a right to a decent share of food, or a law requiring some fairness. |
| 7403 | Grotius ignored elaborate natural law theories, preferring a basic right of self-preservation [Grotius, by Tuck] |
| Full Idea: Grotius said there was a minimum core of morality (based on self-preservation), and disregarded the elaborate accounts of principles of natural law which Aristotelians had always sought to develop. | |
| From: report of Hugo Grotius (On the Law of War and Peace [1625]) by Richard Tuck - Hobbes Ch.1 | |
| A reaction: Aquinas would be the key Aristotelian here. I tend towards the Aristotelian view. If you go for the minimal view, it is not clear why there is a 'right' to self-preservation, rather than a mere desire for it. |
| 23585 | It is permissible in a just cause to capture a place in neutral territory [Grotius] |
| Full Idea: It is permissible for one who is waging a just war to take possession of a place situated in a country free from hostilities. | |
| From: Hugo Grotius (On the Law of War and Peace [1625], II.ii.x), quoted by Michael Walzer - Just and Unjust Wars 15 n | |
| A reaction: This rejects Combatant Equality, allowing the just to do what is morally forbidden to the unjust. |
| 6892 | Moral principles have some validity without a God commanding obedience [Grotius, by Mautner] |
| Full Idea: In the Prolegomena to his work there is a famous statement that moral principles laid down in the work would have some degree of validity even if there was no God commanding obedience. | |
| From: report of Hugo Grotius (On the Law of War and Peace [1625]) by Thomas Mautner - Penguin Dictionary of Philosophy p.229 | |
| A reaction: I am not clear why Grotius felt obliged to qualify his claim with the phrase 'some degree'. I don't see how God's command can affect the 'validity' of morality, or how there can be a middle ground between dependence on and independence of God. |