28 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'). |
| 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? |
| 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. |
| 4983 | There are no rules linking thought and behaviour, because endless other thoughts intervene [Davidson] |
| Full Idea: We know too much about thought and behaviour to trust exact and universal statements linking them. Beliefs and desires issue in behaviour only as modified and mediated by further beliefs and desires, attitudes and attendings, without limit. | |
| From: Donald Davidson (Mental Events [1970], p.217) | |
| A reaction: Now seen as a key objection to behaviourism, and rightly so. However, I am not sure about "without limit", which implies an implausible absolute metaphysical freedom. Davidson goes too far in denying any nomological link between thought and brain. |
| 3529 | Reduction is impossible because mind is holistic and brain isn't [Davidson, by Maslin] |
| Full Idea: Davidson rejects ontological reduction of mental to physical because propositional attitudes are holistic; there must be extensive coherence among someone's attitudes to treat them as a rational person, and this has no counterpart in physical theory. | |
| From: report of Donald Davidson (Mental Events [1970]) by Keith T. Maslin - Introduction to the Philosophy of Mind 7.5 | |
| A reaction: I don't find this view persuasive. We treat the weather in simple terms, even though it is almost infinitely complex. Davidson has a Kantian overconfidence in our rationality. A coherence among the parts is needed to be a tree. |
| 2307 | Anomalous monism says nothing at all about the relationship between mental and physical [Davidson, by Kim] |
| Full Idea: Davidson's anomalous monism says no more about the relationship between the mental and the physical than the claim that all objects with a colour have a shape says about the relationship between colours and shapes. | |
| From: report of Donald Davidson (Mental Events [1970]) by Jaegwon Kim - Mind in a Physical World §1 p.005 | |
| A reaction: Indeed, I find the enthusiasm for property dualism etc. quite baffling, given that we are merely told that mind is 'an anomaly'. I take it to be old fashioned dualism in trendy clothes. |
| 5497 | Mind is outside science, because it is humanistic and partly normative [Davidson, by Lycan] |
| Full Idea: For Davidson, mental types are individuated by considerations that are nonscientific, distinctly humanistic, and part normative, so will not coincide with any types that are designated in scientific terms. | |
| From: report of Donald Davidson (Mental Events [1970]) by William Lycan - Introduction - Ontology p.8 | |
| A reaction: I just don't believe this, mainly because I don't accept that there is a category called 'nonscientific'. All we are saying is that a brain is a hugely complicated object, and we don't properly understand its operations, though we relate to it very well. |
| 4081 | Anomalous monism says causes are events, so the mental and physical are identical, without identical properties [Davidson, by Crane] |
| Full Idea: Davidson's anomalous monism says that events are causes, so we can identify mental and physical events without having to identify their properties. | |
| From: report of Donald Davidson (Mental Events [1970]) by Tim Crane - Elements of Mind 2.18 | |
| A reaction: As Fodor insists, a thing like a mountain has properties at different levels of description. We can have 'property dualism' and full-blown reductive identity. |
| 2321 | If rule-following and reason are 'anomalies', does that make reductionism impossible? [Davidson, by Kim] |
| Full Idea: Davidson takes mental anomalism (that the mind exhibits normativity and rationality), and in particular his claim that there are no laws connecting mental and physical properties, to undermine mind-body reductionism. | |
| From: report of Donald Davidson (Mental Events [1970]) by Jaegwon Kim - Mind in a Physical World §4 p.092 | |
| A reaction: A nice summary of the core idea of property dualism. Personally I expect the whole lot to be reducible, and to follow laws, but the sheer complexity of the brain permanently bars us from actually doing the reduction. |
| 3404 | Davidson claims that mental must be physical, to make mental causation possible [Davidson, by Kim] |
| Full Idea: Davidson's thesis is that if mental events of a particular kind cause physical events of a particular kind, and the two kinds are connected by a law, then they must both be physical kinds. | |
| From: report of Donald Davidson (Mental Events [1970]) by Jaegwon Kim - Philosophy of Mind p.137 | |
| A reaction: Davidson would pretty obviously be right. The whole problem here is the idea of a 'law'. You can only have strict law for simple entities, like particles and natural kinds. The brain is a mess, like weather or explosions. |
| 3405 | If mental causation is lawless, it is only possible if mental events have physical properties [Davidson, by Kim] |
| Full Idea: Since no laws exist connecting mental and physical properties, purely physical laws must do the causal work, which means mental events enter into causal relations only because they possess physical properties that figure in laws. | |
| From: report of Donald Davidson (Mental Events [1970]) by Jaegwon Kim - Philosophy of Mind p.138 | |
| A reaction: Surely no such laws exist 'yet'? I can see no plausible argument that psycho-physical laws are impossible. However, the conclusion of this remark seems right. Interaction requires some sort of equality. |
| 16041 | Supervenience of the mental means physical changes mental, and mental changes physical [Davidson] |
| Full Idea: The supervenience [of mental characteristics on the physical] might be taken to mean that there cannot be two events alike in all physical respects but differing in some mental respect, or an object cannot differ mentally without altering physically. | |
| From: Donald Davidson (Mental Events [1970], I) | |
| A reaction: This is the first occasion on which Davidson introduced his notion of supervenience. Supervenience is often taken to be one-way. The first implies physical causing mental; his second implies that mental causes physical. |
| 6620 | Davidson sees identity as between events, not states, since they are related in causation [Davidson, by Lowe] |
| Full Idea: Davidson's version of the identity theory is couched in terms of events rather than states, because he regards causation as a relation between events. | |
| From: report of Donald Davidson (Mental Events [1970]) by E.J. Lowe - Introduction to the Philosophy of Mind Ch.2 n12 | |
| A reaction: I think it may be more to the point that the mind is a dynamic thing, and so it consists of events rather than states, and hence we want to know what those events are made up from. I think my chair is causing me to rest above the floor… |
| 3429 | Multiple realisability was worse news for physicalism than anomalous monism was [Davidson, by Kim] |
| Full Idea: Davidson's argument about psychophysical anomalism has not been embraced by everyone; multiple realisability of mental properties has had a much greater impact in undermining reductionism (and hence type physicalism). | |
| From: report of Donald Davidson (Mental Events [1970]) by Jaegwon Kim - Philosophy of Mind p.218 | |
| A reaction: My view is that functional states are multiply realisable, but phenomenal states aren't. Fear functions in frogs much as it does in us, but being a frightened frog is nothing like being a frightened human. Their brains are different! |
| 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. |
| 13304 | Learned men gain more in one day than others do in a lifetime [Posidonius] |
| Full Idea: In a single day there lies open to men of learning more than there ever does to the unenlightened in the longest of lifetimes. | |
| From: Posidonius (fragments/reports [c.95 BCE]), quoted by Seneca the Younger - Letters from a Stoic 078 | |
| A reaction: These remarks endorsing the infinite superiority of the educated to the uneducated seem to have been popular in late antiquity. It tends to be the religions which discourage great learning, especially in their emphasis on a single book. |
| 3524 | Causation is either between events, or between descriptions of events [Davidson, by Maslin] |
| Full Idea: According to Davidson analyses of causality proceed at two different levels: at the lower level it holds between events regardless of how they are described; higher level explanations hold between descriptions of events, which pick out properties. | |
| From: report of Donald Davidson (Mental Events [1970]) by Keith T. Maslin - Introduction to the Philosophy of Mind 7.4 |
| 3526 | Whether an event is a causal explanation depends on how it is described [Davidson, by Maslin] |
| Full Idea: Davidson says causal explanations hold between descriptions of events and not between the events themselves, so the possibility of events as explanations depends on how they are described (e.g. a wind collapsing a bridge). | |
| From: report of Donald Davidson (Mental Events [1970]) by Keith T. Maslin - Introduction to the Philosophy of Mind 7.4 |
| 20820 | Time is an interval of motion, or the measure of speed [Posidonius, by Stobaeus] |
| Full Idea: Posidonius defined time thus: it is an interval of motion, or the measure of speed and slowness. | |
| From: report of Posidonius (fragments/reports [c.95 BCE]) by John Stobaeus - Anthology 1.08.42 | |
| A reaction: Hm. Can we define motion or speed without alluding to time? Looks like we have to define them as a conjoined pair, which means we cannot fully understand either of them. |