41 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. |
| 19648 | Since Kant we think we can only access 'correlations' between thinking and being [Meillassoux] |
| Full Idea: The central notion of philosophy since Kant is 'correlation' - that we only ever have access to the correlation between thinking and being, and never to either term considered apart from the other. | |
| From: Quentin Meillassoux (After Finitude; the necessity of contingency [2006], 1) | |
| A reaction: Meillassoux's charge is that philosophy has thereby completely failed to grasp the scientific revolution, which has used mathematics to make objectivity possible. Quine and Putnam would be good examples of what he has in mind. |
| 19674 | The Copernican Revolution decentres the Earth, but also decentres thinking from reality [Meillassoux] |
| Full Idea: The Copernican Revolution is not so much the decentring of observers in the solar system, but (by the mathematizing of nature) the decentring of thought relative to the world within the process of knowledge. | |
| From: Quentin Meillassoux (After Finitude; the necessity of contingency [2006], 5) | |
| A reaction: In other words, I take it, the Copernican Revolution was the discovery of objectivity. That is a very nice addition to my History of Ideas collection. |
| 19657 | In Kant the thing-in-itself is unknowable, but for us it has become unthinkable [Meillassoux] |
| Full Idea: The major shift that has occurred in the conception of thought from Kant's time to ours is from the unknowability of the thing-in-itself to its unthinkability. | |
| From: Quentin Meillassoux (After Finitude; the necessity of contingency [2006], 2) | |
| A reaction: Meillassoux is making the case that philosophy is alienating us more and more from the triumphant realism of the scientific revolution. He says thinking has split from being. He's right. Modern American pragmatists are the worst (not Peirce!). |
| 19675 | Since Kant, philosophers have claimed to understand science better than scientists do [Meillassoux] |
| Full Idea: Ever since Kant, to think science as a philosopher has been to claim that science harbours a meaning other than the one delivered by science itself. | |
| From: Quentin Meillassoux (After Finitude; the necessity of contingency [2006], 5) | |
| A reaction: The point is that science discovered objectivity (via the mathematising of nature), and Kant utterly rejected objectivity, by enmeshing the human mind in every possible scientific claim. This makes Meillassoux and I very cross. |
| 19649 | Since Kant, objectivity is defined not by the object, but by the statement's potential universality [Meillassoux] |
| Full Idea: Since Kant, objectivity is no longer defined with reference to the object in itself, but rather with reference to the possible universality of an objective statement. | |
| From: Quentin Meillassoux (After Finitude; the necessity of contingency [2006], 1) | |
| A reaction: Meillassoux disapproves of this, as a betrayal by philosophers of the scientific revolution, which gave us true objectivity (e.g. about how the world was before humanity). |
| 19666 | If we insist on Sufficient Reason the world will always be a mystery to us [Meillassoux] |
| Full Idea: So long as we continue to believe that there is a reason why things are the way they are rather than some other way, we will construe this world is a mystery, since no such reason will every be vouchsafed to us. | |
| From: Quentin Meillassoux (After Finitude; the necessity of contingency [2006], 4) | |
| A reaction: Giving up sufficient reason sounds like a rather drastic response to this. Put it like this: Will we ever be able to explain absolutely everything? No. So will the world always be a little mysterious to us? Yes, obviously. Is that a problem? No! |
| 19656 | Non-contradiction is unjustified, so it only reveals a fact about thinking, not about reality? [Meillassoux] |
| Full Idea: The principle of non-contradiction itself is without reason, and consequently it can only be the norm for what is thinkable by us, rather than for what is possible in the absolute sense. | |
| From: Quentin Meillassoux (After Finitude; the necessity of contingency [2006], 2) | |
| A reaction: This is not Meillassoux's view, but describes the modern heresy of 'correlationism', which ties all assessments of how reality is to our capacity to think about it. Personally I take logical non-contradiction to derive from non-contradiction in nature. |
| 10845 | To be true a sentence must express a proposition, and not be ambiguous or vague or just expressive [Lewis] |
| Full Idea: Sentences or assertions can be derivately called true, if they succeed in expressing determinate propositions. A sentence can be ambiguous or vague or paradoxical or ungrounded or not declarative or a mere expression of feeling. | |
| From: David Lewis (Forget the 'correspondence theory of truth' [2001], p.276) | |
| A reaction: Lewis has, of course, a peculiar notion of what a proposition is - it's a set of possible worlds. I, with my more psychological approach, take a proposition to be a particular sort of brain event. |
| 10847 | Truthmakers are about existential grounding, not about truth [Lewis] |
| Full Idea: Instances of the truthmaker principle are equivalent to biconditionals not about truth but about the existential grounding of all manner of other things; the flying pigs, or what-have-you. | |
| From: David Lewis (Forget the 'correspondence theory of truth' [2001]) | |
| A reaction: The question then is what the difference is between 'existential grounding' and 'truth'. There wouldn't seem to be any difference at all if the proposition in question was a simple existential claim. |
| 10846 | Truthmaker is correspondence, but without the requirement to be one-to-one [Lewis] |
| Full Idea: The truthmaker principle seems to be a version of the correspondence theory of truth, but differs mostly in denying that the correspondence of truths to facts must be one-to-one. | |
| From: David Lewis (Forget the 'correspondence theory of truth' [2001], p.277) | |
| A reaction: In other words, several different sentences might have exactly the same truthmaker. |
| 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. |
| 19663 | We can allow contradictions in thought, but not inconsistency [Meillassoux] |
| Full Idea: For contemporary logicians, it is not non-contradiction that provides the criterion for what is thinkable, but rather inconsistency. | |
| From: Quentin Meillassoux (After Finitude; the necessity of contingency [2006], 3) | |
| A reaction: The point is that para-consistent logic might permit isolated contradictions (as true) within a system, but it is only contradiction across the system (inconsistencies) which make the system untenable. |
| 19664 | Paraconsistent logics are to prevent computers crashing when data conflicts [Meillassoux] |
| Full Idea: Paraconsistent logics were only developed in order to prevent computers, such as expert medical systems, from deducing anything whatsoever from contradictory data, because of the principle of 'ex falso quodlibet'. | |
| From: Quentin Meillassoux (After Finitude; the necessity of contingency [2006], 3) |
| 19665 | Paraconsistent logic is about statements, not about contradictions in reality [Meillassoux] |
| Full Idea: Paraconsistent logics are only ever dealing with contradictions inherent in statements about the world, never with the real contradictions in the world. | |
| From: Quentin Meillassoux (After Finitude; the necessity of contingency [2006], 3) | |
| A reaction: Thank goodness for that! I can accept that someone in a doorway is both in the room and not in the room, but not that they are existing in a real state of contradiction. I fear that a few daft people embrace the logic as confirming contradictory reality. |
| 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? |
| 19677 | What is mathematically conceivable is absolutely possible [Meillassoux] |
| Full Idea: We must establish the thesis that what is mathematically conceivable is absolutely possible. | |
| From: Quentin Meillassoux (After Finitude; the necessity of contingency [2006], 5) | |
| A reaction: The truth of this thesis would permanently establish mathematics as the only possible language of science. Personally I have no idea how you could prove or assess such a thesis. It is a lovely speculation, though. 'The structure of the possible' (p,127) |
| 19659 | The absolute is the impossibility of there being a necessary existent [Meillassoux] |
| Full Idea: We maintain that it is absolutely necessary that every entity might not exist. ...The absolute is the absolute impossibility of a necessary being. | |
| From: Quentin Meillassoux (After Finitude; the necessity of contingency [2006], 3) | |
| A reaction: This is the main thesis of his book. The usual candidates for necessary existence are God, and mathematical objects. I am inclined to agree with Meillassoux. |
| 19662 | It is necessarily contingent that there is one thing rather than another - so something must exist [Meillassoux] |
| Full Idea: It is necessary that there be something rather than nothing because it is necessarily contingent that there is something rather than something else. | |
| From: Quentin Meillassoux (After Finitude; the necessity of contingency [2006], 3) | |
| A reaction: The great charm of metaphysics is the array of serious answers to the question of why there is something rather than nothing. You'll need to read Meillassoux's book to understand this one. |
| 19654 | We must give up the modern criterion of existence, which is a correlation between thought and being [Meillassoux] |
| Full Idea: It is incumbent upon us to break with the ontological requisite of the moderns, according to which 'to be is to be a correlate'. | |
| From: Quentin Meillassoux (After Finitude; the necessity of contingency [2006], 2) | |
| A reaction: He blames Kant for this pernicious idea, which has driven philosophy away from realist science, when it should be supporting and joining it. As a realist I agree, and find Meillassoux very illuminating on the subject. |
| 19660 | Possible non-being which must be realised is 'precariousness'; absolute contingency might never not-be [Meillassoux] |
| Full Idea: My term 'precariousness' designates a possibility of not-being which must eventually be realised. By contrast, absolute contingency designates a pure possibility; one which may never be realised. | |
| From: Quentin Meillassoux (After Finitude; the necessity of contingency [2006], 3) | |
| A reaction: I thoroughly approve of this distinction, because I have often enountered the assumption that all contingency is precariousness, and I have never seen why that should be so. In Aquinas's Third Way, for example. The 6 on a die may never come up. |
| 19671 | The idea of chance relies on unalterable physical laws [Meillassoux] |
| Full Idea: The very notion of chance is only conceivable on condition that there are unalterable physical laws. | |
| From: Quentin Meillassoux (After Finitude; the necessity of contingency [2006], 4) | |
| A reaction: Laws might be contingent, even though they never alter. Chance in horse racing relies on the stability of whole institution of horse racing. |
| 19651 | Unlike speculative idealism, transcendental idealism assumes the mind is embodied [Meillassoux] |
| Full Idea: What distinguishes transcendental idealism from speculative idealism is the fact that the former does not posit the existence of the transcendental subject apart from its bodily individuation. | |
| From: Quentin Meillassoux (After Finitude; the necessity of contingency [2006], 1) | |
| A reaction: These modern French philosophers explain things so much more clearly than the English! The 'speculative' version is seen in Berkeley. On p.17 he says transcendental idealism is 'civilised', and speculative idealism is 'uncouth'. |
| 19647 | The aspects of objects that can be mathematical allow it to have objective properties [Meillassoux] |
| Full Idea: All aspects of the object that can give rise to a mathematical thought rather than to a perception or a sensation can be meaningfully turned into the properties of the thing not only as it is with me, but also as it is without me. | |
| From: Quentin Meillassoux (After Finitude; the necessity of contingency [2006], 1) | |
| A reaction: This is Meillassoux's spin on the primary/secondary distinction, which he places at the heart of the scientific revolution. Cartesian dualism offers a separate space for the secondary qualities. He is appalled when philosophers reject the distinction. |
| 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. |
| 19652 | How can we mathematically describe a world that lacks humans? [Meillassoux] |
| Full Idea: How is mathematical discourse able to describe a reality where humanity is absent? | |
| From: Quentin Meillassoux (After Finitude; the necessity of contingency [2006], 1) | |
| A reaction: He is referring to the prehistoric world. He takes this to be a key question about the laws of nature. We extrapolate mathematically from the experienced world, relying on the stability of the laws. Must they be necessary to be stable? No, it seems. |
| 19668 | Hume's question is whether experimental science will still be valid tomorrow [Meillassoux] |
| Full Idea: Hume's question can be formulated as follows: can we demonstrate that the experimental science which is possible today will still be possible tomorrow? | |
| From: Quentin Meillassoux (After Finitude; the necessity of contingency [2006], 4) | |
| A reaction: Could there be deep universal changes going on in nature which science could never, even in principle, detect? |
| 19650 | The transcendental subject is not an entity, but a set of conditions making science possible [Meillassoux] |
| Full Idea: The transcendental subject simply cannot be said to exist; which is to say that the subject is not an entity, but rather a set of conditions rendering objective scientific knowledge of entities possible. | |
| From: Quentin Meillassoux (After Finitude; the necessity of contingency [2006], 1) | |
| A reaction: Meillassoux treats this as part of the Kantian Disaster, which made an accurate account of the scientific revolution impossible for philosophers. Kant's ego seems to have primarily an epistemological role. |
| 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. |
| 19667 | If the laws of nature are contingent, shouldn't we already have noticed it? [Meillassoux] |
| Full Idea: The standard objection is that if the laws of nature were actually contingent, we would already have noticed it. | |
| From: Quentin Meillassoux (After Finitude; the necessity of contingency [2006], 4) | |
| A reaction: Meillassoux offers a sustained argument that the laws of nature are necessarily contingent. In Idea 19660 he distinguishes contingencies that must change from those that merely could change. |
| 19670 | Why are contingent laws of nature stable? [Meillassoux] |
| Full Idea: We must ask how we are to explain the manifest stability of physical laws, given that we take these to be contingent? | |
| From: Quentin Meillassoux (After Finitude; the necessity of contingency [2006], 4) | |
| A reaction: Meissalloux offers a very deep and subtle answer to this question... It is based on the possibilities of chaos being an uncountable infinity... It is a very nice question, which physicists might be able to answer, without help from philosophy. |
| 19653 | The ontological proof of a necessary God ensures a reality external to the mind [Meillassoux] |
| Full Idea: Since Descartes conceives of God as existing necessarily, whether I exist to think of him or not, Descartes assures me of a possible access to an absolute reality - a Great Outdoors that is not a correlate of my thought. | |
| From: Quentin Meillassoux (After Finitude; the necessity of contingency [2006], 2) | |
| A reaction: His point is that the ontological argument should be seen as part of the scientific revolution, and not an anomaly within it. Interesting. |
| 19658 | Now that the absolute is unthinkable, even atheism is just another religious belief (though nihilist) [Meillassoux] |
| Full Idea: Once the absolute has become unthinkable, even atheism, which also targets God's inexistence in the manner of an absolute, is reduced to a mere belief, and hence to a religion, albeit of the nihilist kind. | |
| From: Quentin Meillassoux (After Finitude; the necessity of contingency [2006], 2) | |
| A reaction: An interesting claim. Rather hard to agree or disagree, though the idea that atheism must qualify as a religion seems odd. If it is unqualified it does have the grand quality of a religion, but if it is fallibilist it just seems like an attitude. |