35 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. |
14611 | Metaphysics should avoid talk of past, present or future [Smart] |
Full Idea: Metaphysics should not be cosmically parochial. It should eschew tensed languages. | |
From: J.J.C. Smart (The Tenseless Theory of Time [2008], 1) | |
A reaction: This is quite an engaging reason to be an eternalist (or B-theorist) about time. Presumably we can still believe in tensed time, as long as we recognise that metaphysics itself is a timeless subject. |
17070 | Coherence is consilience, simplicity, analogy, and fitting into a web of belief [Smart] |
Full Idea: I shall make use of the admittedly imprecise notions of consilience, simplicity, analogy and fitting into a web of belief, or in short of 'coherence'. | |
From: J.J.C. Smart (Explanation - Opening Address [1990], p.06) | |
A reaction: Coherence sounds like a family of tests, rather than a single unified concept. I still like coherence, though. |
17072 | We need comprehensiveness, as well as self-coherence [Smart] |
Full Idea: Not mere self-coherence, but comprehensiveness belongs to the notion of coherence. | |
From: J.J.C. Smart (Explanation - Opening Address [1990], p.07) |
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'). |
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. |
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. |
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? |
16062 | A necessary relation between fact-levels seems to be a further irreducible fact [Lynch/Glasgow] |
Full Idea: It seems unavoidable that the facts about logically necessary relations between levels of facts are themselves logically distinct further facts, irreducible to the microphysical facts. | |
From: Lynch,MP/Glasgow,JM (The Impossibility of Superdupervenience [2003], C) | |
A reaction: I'm beginning to think that rejecting every theory of reality that is proposed by carefully exposing some infinite regress hidden in it is a rather lazy way to do philosophy. Almost as bad as rejecting anything if it can't be defined. |
16061 | If some facts 'logically supervene' on some others, they just redescribe them, adding nothing [Lynch/Glasgow] |
Full Idea: Logical supervenience, restricted to individuals, seems to imply strong reduction. It is said that where the B-facts logically supervene on the A-facts, the B-facts simply re-describe what the A-facts describe, and the B-facts come along 'for free'. | |
From: Lynch,MP/Glasgow,JM (The Impossibility of Superdupervenience [2003], C) | |
A reaction: This seems to be taking 'logically' to mean 'analytically'. Presumably an entailment is logically supervenient on its premisses, and may therefore be very revealing, even if some people think such things are analytic. |
16060 | Nonreductive materialism says upper 'levels' depend on lower, but don't 'reduce' [Lynch/Glasgow] |
Full Idea: The root intuition behind nonreductive materialism is that reality is composed of ontologically distinct layers or levels. …The upper levels depend on the physical without reducing to it. | |
From: Lynch,MP/Glasgow,JM (The Impossibility of Superdupervenience [2003], B) | |
A reaction: A nice clear statement of a view which I take to be false. This relationship is the sort of thing that drives people fishing for an account of it to use the word 'supervenience', which just says two things seem to hang out together. Fluffy materialism. |
16064 | The hallmark of physicalism is that each causal power has a base causal power under it [Lynch/Glasgow] |
Full Idea: Jessica Wilson (1999) says what makes physicalist accounts different from emergentism etc. is that each individual causal power associated with a supervenient property is numerically identical with a causal power associated with its base property. | |
From: Lynch,MP/Glasgow,JM (The Impossibility of Superdupervenience [2003], n 11) | |
A reaction: Hence the key thought in so-called (serious, rather than self-evident) 'emergentism' is so-called 'downward causation', which I take to be an idle daydream. |
17073 | I simply reject evidence, if it is totally contrary to my web of belief [Smart] |
Full Idea: The simplest way of fitting the putative observed phenomena of telepathy or clairvoyance into my web of belief is to refuse to take them at face value. | |
From: J.J.C. Smart (Explanation - Opening Address [1990], p.07-8) | |
A reaction: Love it. It is very disconcerting for the sceptical naturalist to be faced with adamant claims that the paranormal has occurred, but my response is exactly the same as Smart's. I reject the reports, no matter how passionately they are asserted. |
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. |
17077 | The height of a flagpole could be fixed by its angle of shadow, but that would be very unusual [Smart] |
Full Idea: You could imagine a person using the angle from a theodolite to decide a suitable spot to cut the height of the flagpole, …but since such circumstances would be very unusual we naturally say the flagpole subtends the angle because of its height. | |
From: J.J.C. Smart (Explanation - Opening Address [1990], p.14) | |
A reaction: [compressed; he mentions Van Fraassen 1980:132-3 for a similar point] As a response this seems a bit lame, if the direction is fixed by what is 'usual'. I think the key point is that the direction of explanation is one way or the other, not both. |
17078 | Universe expansion explains the red shift, but not vice versa [Smart] |
Full Idea: The theory of the expansion of the universe renders the red shift no longer puzzling, whereas he expansion of the universe is hardly rendered less puzzling by facts about the red shift. | |
From: J.J.C. Smart (Explanation - Opening Address [1990], p.15) | |
A reaction: The direction of explanation is, I take it, made obvious by the direction of causation, with questions about what is 'puzzling' as mere side-effects. |
17061 | Explanation of a fact is fitting it into a system of beliefs [Smart] |
Full Idea: I want to characterise explanation of some fact as a matter of fitting belief in this fact into a system of beliefs. | |
From: J.J.C. Smart (Explanation - Opening Address [1990], p.02) | |
A reaction: Sounds good to me. Simple facts slot straight into daily beliefs, and deep obscure facts are explained when we hook them up to things we have already grasped. Quark theory fits into prior physics of forces, properties etc. |
17074 | Explanations are bad by fitting badly with a web of beliefs, or fitting well into a bad web [Smart] |
Full Idea: An explanation may be bad if it fits only into a bad web of belief. It can also be bad if it fits into a (possibly good) web of belief in a bad sort of way. | |
From: J.J.C. Smart (Explanation - Opening Address [1990], p.09) | |
A reaction: Nice. If you think someone has an absurd web of beliefs, then it counts against some belief (for you) if it fits beautifully into the other person's belief system. Judgement of coherence comes in at different levels. |
17076 | Deducing from laws is one possible way to achieve a coherent explanation [Smart] |
Full Idea: The Hempelian deductive-nomological model of explanation clearly fits in well with the notion of explanation in terms of coherence. One way of fitting a belief into a system is to show that it is deducible from other beliefs. | |
From: J.J.C. Smart (Explanation - Opening Address [1990], p.13) | |
A reaction: Smart goes on to reject the law-based deductive approach, for familiar reasons, but at least it has something in common with the Smart view of explanation, which is the one I like. |
17071 | An explanation is better if it also explains phenomena from a different field [Smart] |
Full Idea: One explanation will be a better explanation that another if it also explains a set of phenomena from a different field ('consilience'). | |
From: J.J.C. Smart (Explanation - Opening Address [1990], p.07) | |
A reaction: This would count as 'unexpected accommodation', rather than prediction. It is a nice addition to Lipton's comparison of mere accommodation versus prediction as criteria. It sounds like a strong criterion for a persuasive explanation. |
17062 | If scientific explanation is causal, that rules out mathematical explanation [Smart] |
Full Idea: I class mathematical explanation with scientific explanation. This would be resisted by those who, unlike me, regard the notion of causation as essential to scientific explanation. | |
From: J.J.C. Smart (Explanation - Opening Address [1990], p.02-3) | |
A reaction: I aim to champion mathematical explanation, in terms of axioms etc., so I am realising that my instinctive attraction to exclusively causal explanation won't do. What explanation needs is a direction of dependence. |
17075 | Scientific explanation tends to reduce things to the unfamiliar (not the familiar) [Smart] |
Full Idea: The history of science suggests that most often explanation is reduction to the unfamiliar. | |
From: J.J.C. Smart (Explanation - Opening Address [1990], p.11) | |
A reaction: Boyle was keen to reduce things to the familiar, but that was early days for science, and some nasty shocks were coming our way. What would Boyle make of quantum non-locality? |
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. |
22405 | Negative utilitarianism implies that the world should be destroyed, to avoid future misery [Smart] |
Full Idea: The doctrine of negative utilitarianism (that we should concern ourselves with the minimisation of suffering, rather than the maximisation of happiness) ...means we should support a tyrant who explodes the world, to prevent infinite future misery. | |
From: J.J.C. Smart (Outline of a System of Utilitarianism [1973], 5) | |
A reaction: That only seems to imply that the negative utilitarian rule needs supplementary rules. We are too fond of looking for one single moral rule that guides everything. |
22404 | Any group interested in ethics must surely have a sentiment of generalised benevolence [Smart] |
Full Idea: A utilitarian can appeal to the sentiment of generalised benevolence, which is surely present in any group with whom it is profitable to discuss ethical questions. | |
From: J.J.C. Smart (Outline of a System of Utilitarianism [1973], I) | |
A reaction: But ethics is not intended only for those who are interested in ethics. If this is the basics of ethics, then we must leave the mafia to pursue its sordid activities without criticism. Their lack of sympathy seems to be their good fortune. |
14613 | Special relativity won't determine a preferred frame, but we can pick one externally [Smart] |
Full Idea: Though special relativity does not determine a preferred frame of reference, it does not rule out the possibility of a frame being determined from outside the theory. Perhaps we should prefer a frame where background radiation is equal in all directions. | |
From: J.J.C. Smart (The Tenseless Theory of Time [2008], 3) | |
A reaction: Of course this is a mere philosopher offering the escape clause, and not some Nobel-winning physicist, but I start from the assumption that this idea is plausible, and I am unmoved by the contempt for presentism among relativity geeks. |
17063 | Unlike Newton, Einstein's general theory explains the perihelion of Mercury [Smart] |
Full Idea: Newtonian celestial mechanics does not explain the advance of the perihelion of Mercury, while Einstein's general theory of relativity does. | |
From: J.J.C. Smart (Explanation - Opening Address [1990], p.03) | |
A reaction: A perfect example of why explanation is the central concept in science, and probably in all epistemological activity. The desire to know is the desire for an explanation. Once the explanation is obvious, we know. |
14615 | If time flows, then 'how fast does it flow?' is a tricky question [Smart] |
Full Idea: If it is said that time flows, then it seems that the question 'how fast does it flow?' is a devastating one for the A-theorist. | |
From: J.J.C. Smart (The Tenseless Theory of Time [2008], 5) | |
A reaction: This is one of the basic landmarks in any debate on time. Time can't be understood by analogy with anything else (such as a river) it seems. |
14614 | The past, present, future and tenses of A-theory are too weird, and should be analysed indexically [Smart] |
Full Idea: The main objections to the A-theory are due to the metaphysical mysteriousness of the A-theory ideas of past, present and future, and also tenses, and to the greater plausibility of analyzing them as indexicals. | |
From: J.J.C. Smart (The Tenseless Theory of Time [2008], 3) | |
A reaction: When it comes to time, every theory that has ever been though of is deeply weird, so the basic objection doesn't bother me. Analysing as indexicals just seems to be a technical way of denying reality to the present. |