38 ideas
| 17926 | Rejecting double negation elimination undermines reductio proofs [Colyvan] |
| Full Idea: The intuitionist rejection of double negation elimination undermines the important reductio ad absurdum proof in classical mathematics. | |
| From: Mark Colyvan (Introduction to the Philosophy of Mathematics [2012], 1.1.3) |
| 17925 | Showing a disproof is impossible is not a proof, so don't eliminate double negation [Colyvan] |
| Full Idea: In intuitionist logic double negation elimination fails. After all, proving that there is no proof that there can't be a proof of S is not the same thing as having a proof of S. | |
| From: Mark Colyvan (Introduction to the Philosophy of Mathematics [2012], 1.1.3) | |
| A reaction: I do like people like Colyvan who explain things clearly. All of this difficult stuff is understandable, if only someone makes the effort to explain it properly. |
| 17924 | Excluded middle says P or not-P; bivalence says P is either true or false [Colyvan] |
| Full Idea: The law of excluded middle (for every proposition P, either P or not-P) must be carefully distinguished from its semantic counterpart bivalence, that every proposition is either true or false. | |
| From: Mark Colyvan (Introduction to the Philosophy of Mathematics [2012], 1.1.3) | |
| A reaction: So excluded middle makes no reference to the actual truth or falsity of P. It merely says P excludes not-P, and vice versa. |
| 17929 | Löwenheim proved his result for a first-order sentence, and Skolem generalised it [Colyvan] |
| Full Idea: Löwenheim proved that if a first-order sentence has a model at all, it has a countable model. ...Skolem generalised this result to systems of first-order sentences. | |
| From: Mark Colyvan (Introduction to the Philosophy of Mathematics [2012], 2.1.2) |
| 17930 | Axioms are 'categorical' if all of their models are isomorphic [Colyvan] |
| Full Idea: A set of axioms is said to be 'categorical' if all models of the axioms in question are isomorphic. | |
| From: Mark Colyvan (Introduction to the Philosophy of Mathematics [2012], 2.1.2) | |
| A reaction: The best example is the Peano Axioms, which are 'true up to isomorphism'. Set theory axioms are only 'quasi-isomorphic'. |
| 17928 | Ordinal numbers represent order relations [Colyvan] |
| Full Idea: Ordinal numbers represent order relations. | |
| From: Mark Colyvan (Introduction to the Philosophy of Mathematics [2012], 1.2.3 n17) |
| 17923 | Intuitionists only accept a few safe infinities [Colyvan] |
| Full Idea: For intuitionists, all but the smallest, most well-behaved infinities are rejected. | |
| From: Mark Colyvan (Introduction to the Philosophy of Mathematics [2012], 1.1.3) | |
| A reaction: The intuitionist idea is to only accept what can be clearly constructed or proved. |
| 17941 | Infinitesimals were sometimes zero, and sometimes close to zero [Colyvan] |
| Full Idea: The problem with infinitesimals is that in some places they behaved like real numbers close to zero but in other places they behaved like zero. | |
| From: Mark Colyvan (Introduction to the Philosophy of Mathematics [2012], 7.1.2) | |
| A reaction: Colyvan gives an example, of differentiating a polynomial. |
| 17922 | Reducing real numbers to rationals suggested arithmetic as the foundation of maths [Colyvan] |
| Full Idea: Given Dedekind's reduction of real numbers to sequences of rational numbers, and other known reductions in mathematics, it was tempting to see basic arithmetic as the foundation of mathematics. | |
| From: Mark Colyvan (Introduction to the Philosophy of Mathematics [2012], 1.1.1) | |
| A reaction: The reduction is the famous Dedekind 'cut'. Nowadays theorists seem to be more abstract (Category Theory, for example) instead of reductionist. |
| 17936 | Transfinite induction moves from all cases, up to the limit ordinal [Colyvan] |
| Full Idea: Transfinite inductions are inductive proofs that include an extra step to show that if the statement holds for all cases less than some limit ordinal, the statement also holds for the limit ordinal. | |
| From: Mark Colyvan (Introduction to the Philosophy of Mathematics [2012], 5.2.1 n11) |
| 17940 | Most mathematical proofs are using set theory, but without saying so [Colyvan] |
| Full Idea: Most mathematical proofs, outside of set theory, do not explicitly state the set theory being employed. | |
| From: Mark Colyvan (Introduction to the Philosophy of Mathematics [2012], 7.1.1) |
| 17931 | Structuralism say only 'up to isomorphism' matters because that is all there is to it [Colyvan] |
| Full Idea: Structuralism is able to explain why mathematicians are typically only interested in describing the objects they study up to isomorphism - for that is all there is to describe. | |
| From: Mark Colyvan (Introduction to the Philosophy of Mathematics [2012], 3.1.2) |
| 17932 | If 'in re' structures relies on the world, does the world contain rich enough structures? [Colyvan] |
| Full Idea: In re structuralism does not posit anything other than the kinds of structures that are in fact found in the world. ...The problem is that the world may not provide rich enough structures for the mathematics. | |
| From: Mark Colyvan (Introduction to the Philosophy of Mathematics [2012], 3.1.2) | |
| A reaction: You can perceive a repeating pattern in the world, without any interest in how far the repetitions extend. |
| 17943 | Probability supports Bayesianism better as degrees of belief than as ratios of frequencies [Colyvan] |
| Full Idea: Those who see probabilities as ratios of frequencies can't use Bayes's Theorem if there is no objective prior probability. Those who accept prior probabilities tend to opt for a subjectivist account, where probabilities are degrees of belief. | |
| From: Mark Colyvan (Introduction to the Philosophy of Mathematics [2012], 9.1.8) | |
| A reaction: [compressed] |
| 17939 | Mathematics can reveal structural similarities in diverse systems [Colyvan] |
| Full Idea: Mathematics can demonstrate structural similarities between systems (e.g. missing population periods and the gaps in the rings of Saturn). | |
| From: Mark Colyvan (Introduction to the Philosophy of Mathematics [2012], 6.3.2) | |
| A reaction: [Colyvan expounds the details of his two examples] It is these sorts of results that get people enthusiastic about the mathematics embedded in nature. A misunderstanding, I think. |
| 17938 | Mathematics can show why some surprising events have to occur [Colyvan] |
| Full Idea: Mathematics can show that under a broad range of conditions, something initially surprising must occur (e.g. the hexagonal structure of honeycomb). | |
| From: Mark Colyvan (Introduction to the Philosophy of Mathematics [2012], 6.3.2) |
| 17934 | Proof by cases (by 'exhaustion') is said to be unexplanatory [Colyvan] |
| Full Idea: Another style of proof often cited as unexplanatory are brute-force methods such as proof by cases (or proof by exhaustion). | |
| From: Mark Colyvan (Introduction to the Philosophy of Mathematics [2012], 5.2.1) |
| 17933 | Reductio proofs do not seem to be very explanatory [Colyvan] |
| Full Idea: One kind of proof that is thought to be unexplanatory is the 'reductio' proof. | |
| From: Mark Colyvan (Introduction to the Philosophy of Mathematics [2012], 5.2.1) | |
| A reaction: Presumably you generate a contradiction, but are given no indication of why the contradiction has arisen? Tracking back might reveal the source of the problem? Colyvan thinks reductio can be explanatory. |
| 17935 | If inductive proofs hold because of the structure of natural numbers, they may explain theorems [Colyvan] |
| Full Idea: It might be argued that any proof by induction is revealing the explanation of the theorem, namely, that it holds by virtue of the structure of the natural numbers. | |
| From: Mark Colyvan (Introduction to the Philosophy of Mathematics [2012], 5.2.1) | |
| A reaction: This is because induction characterises the natural numbers, in the Peano Axioms. |
| 17942 | Can a proof that no one understands (of the four-colour theorem) really be a proof? [Colyvan] |
| Full Idea: The proof of the four-colour theorem raises questions about whether a 'proof' that no one understands is a proof. | |
| From: Mark Colyvan (Introduction to the Philosophy of Mathematics [2012], 9.1.6) | |
| A reaction: The point is that the theorem (that you can colour countries on a map with just four colours) was proved with the help of a computer. |
| 17937 | Mathematical generalisation is by extending a system, or by abstracting away from it [Colyvan] |
| Full Idea: One type of generalisation in mathematics extends a system to go beyond what is was originally set up for; another kind involves abstracting away from some details in order to capture similarities between different systems. | |
| From: Mark Colyvan (Introduction to the Philosophy of Mathematics [2012], 5.2.2) |
| 12157 | Kant gave form and status to aesthetics, and Hegel gave it content [Kant, by Scruton] |
| Full Idea: Kant gave form and status to aesthetics, and Hegel endowed it with content. | |
| From: report of Immanuel Kant (Critique of Judgement I: Aesthetic [1790]) by Roger Scruton - Recent Aesthetics in England and America p.3 |
| 20346 | The aesthetic attitude is a matter of disinterestedness [Kant, by Wollheim] |
| Full Idea: The aesthetic attitude is defined by Kant in terms of disinterestedness. | |
| From: report of Immanuel Kant (Critique of Judgement I: Aesthetic [1790]) by Richard Wollheim - Art and Its Objects 54 | |
| A reaction: This is presumably, mainly, to explain our enjoyment of the miseries of tragedy. We just give ourselves up to a merry jig by Haydn. |
| 18547 | Only rational beings can experience beauty [Kant, by Scruton] |
| Full Idea: Kant is surely right that the experience of beauty, like the judgements in which it issues, is the prerogative of rational beings. | |
| From: report of Immanuel Kant (Critique of Judgement I: Aesthetic [1790]) by Roger Scruton - Beauty: a very short introduction 1 | |
| A reaction: I'm not sure how Scruton can say that Kant is 'surely right'. It is an interesting speculation. Are we to dogmatically affirm that bees get no aesthetic thrill when they spot a promising flower? Something in their little brains attracts them. |
| 24172 | It is hard to see why we would have developed Kant's 'disinterested' aesthetic attitude [Cochrane on Kant] |
| Full Idea: The Kantian notion of disinterest isolated aesthetic value from the rest of our lives. It is hard to understand why we should have developed a tendency that is detached from our everyday practical purposes. | |
| From: comment on Immanuel Kant (Critique of Judgement I: Aesthetic [1790], §2) by Tom Cochrane - The Aesthetic Value of the World 1.4 | |
| A reaction: Cochrane always seeks an evolutionary framework for accounts of aesthetics, and I agree with him. That doesn't devalue them. The best things in life, like piano music, are obviously offshoots of things which evolved for other reasons. |
| 20408 | With respect to the senses, taste is an entirely personal matter [Kant] |
| Full Idea: With regard to the agreeable, the principle Everyone has his own taste (of the senses) is valid. | |
| From: Immanuel Kant (Critique of Judgement I: Aesthetic [1790], CUP 7 5:212), quoted by Elizabeth Schellekens - Immanuel Kant (aesthetics) 1 | |
| A reaction: This is a preliminary concession, and he goes on to defend more objective views of taste. |
| 20409 | When we judge beauty, it isn't just personal; we judge on behalf of everybody [Kant] |
| Full Idea: It is ridiculous if someone justifies his tast by saying 'this object is beautiful for me'. . .If he pronounces that something is beautiful, then he expects the very same satisfaction of others: he judges not merely for himself, but for everyone. | |
| From: Immanuel Kant (Critique of Judgement I: Aesthetic [1790], CUP 7 5:213), quoted by Elizabeth Schellekens - Immanuel Kant (aesthetics) 1 | |
| A reaction: For Kant this would also be the hallmark of rationality - that we expect, or hope for, a consensus when we express a rational judgement. But this expectation is far less in cases of beauty. We do not expect total agreement from very tasteful people. |
| 20411 | Saying everyone has their own taste destroys the very idea of taste [Kant] |
| Full Idea: To say thast 'Everyone has his special taste' would be to dismiss the very possibility of aesthetic taste, and to deny that there could be aesthetic judgement 'that could make a rightful claim to the assent of everyone'. | |
| From: Immanuel Kant (Critique of Judgement I: Aesthetic [1790], CUP 7 5:213), quoted by Elizabeth Schellekens - Immanuel Kant (aesthetics) 2.2 | |
| A reaction: I am a great believer in the objectivity of taste (within sensible reason). But the great evidence against it is the shifting standards of taste over the centuries. Nineteenth century collectors wasted fortunes on inferior works, it seems to us. |
| 24170 | Kant thinks beauty ignores its objects, because it is only 'form' engaging with mind [Cochrane on Kant] |
| Full Idea: Kant thinks that the ideal of beauty requires no concept of what the object is. Universality demands that appreciation be purely a matter of the way the form of the object fits one's cognitive machinery. | |
| From: comment on Immanuel Kant (Critique of Judgement I: Aesthetic [1790]) by Tom Cochrane - The Aesthetic Value of the World 1.3 | |
| A reaction: This confirms further my increasingly negative view of Kant. Everything in him points to idealism (despite denials by his fans), and via Hegel we arrive at the idea that our values are all 'cultural constructs', rather than responses to reality. |
| 22711 | The beautiful is not conceptualised as moral, but it symbolises or resembles goodness [Kant, by Murdoch] |
| Full Idea: Kant insists that the beautiful must not be tainted with the good (that is, not conceptualised in any way which would bring it into the sphere of moral judgement) yet he says that the beautiful symbolises the good, it is an analogy of the good. | |
| From: report of Immanuel Kant (Critique of Judgement I: Aesthetic [1790]) by Iris Murdoch - The Sublime and the Good p.209 | |
| A reaction: Kant evidently wanted a very pure view of the aesthetic experience, drained of any overlapping feelings or beliefs. I'm not sure I understand how the beautiful can symbolise or be analogous to the good, while being devoid of it. |
| 4025 | Kant saw beauty as a sort of disinterested pleasure, which has become separate from the good [Kant, by Taylor,C] |
| Full Idea: Kant, in his third critique, defined beauty in terms of a certain kind of disinterested pleasure;….this is the basis for a declaration of independence of the beautiful relative to the good. | |
| From: report of Immanuel Kant (Critique of Judgement I: Aesthetic [1790]) by Charles Taylor - Sources of the Self §23.1 | |
| A reaction: This is a rebellion against the Greeks, especially Plato, and prepares the ground for the idea of 'art for art's sake'. Personally, I'm with Plato. |
| 20412 | Beauty is only judged in pure contemplation, and not with something else at stake [Kant] |
| Full Idea: If the question is whether something is beautiful, one does not want to know whether there is something that is or that could be at stake, for us or for someone else, in the existence of the thing, but rather how we judge it in mere contemplation. | |
| From: Immanuel Kant (Critique of Judgement I: Aesthetic [1790], CUP 2 5:204), quoted by Elizabeth Schellekens - Immanuel Kant (aesthetics) 2.3 | |
| A reaction: This evidently denies that function has anything to do with beauty, and seems to be a prelude to 'art for art's sake'. But a running cheetah cannot be separated from the sheer efficiencey and focus of the performance. |
| 22046 | The mathematical sublime is immeasurable greatness; the dynamical sublime is overpowering [Kant, by Pinkard] |
| Full Idea: Kant distinguished the 'mathematical' and 'dynamical' sublime. The former involves immeasurable greatness (or smallness) such that we cannot even present them to ourselves. The latter is of something large and overpowering, which we can morally resist. | |
| From: report of Immanuel Kant (Critique of Judgement I: Aesthetic [1790]) by Terry Pinkard - German Philosophy 1760-1860 13 | |
| A reaction: Presumably Cantor revealed the full extent of the mathematical sublime ('heaven', according to Hilbert). We await the comet that destroys the Earth to fully experience the other one. |
| 21458 | The sublime is a moral experience [Kant, by Gardner] |
| Full Idea: The sublime is understood by Kant as a moral experience. | |
| From: report of Immanuel Kant (Critique of Judgement I: Aesthetic [1790], 28-9) by Sebastian Gardner - Kant and the Critique of Pure Reason 09 'Judgment' | |
| A reaction: Gardner give the source in Kant. I can't accept that the initial experience of the sublime is moral in character. It could easily acquire a moral character after contemplation by someone who had such inclinations. |
| 5643 | Aesthetic values are not objectively valid, but we must treat them as if they are [Kant, by Scruton] |
| Full Idea: The 'Critique of Judgement' argues, then, not for the objective validity of aesthetic values, but for the fact that we must think of them as objectively valid. | |
| From: report of Immanuel Kant (Critique of Judgement I: Aesthetic [1790]) by Roger Scruton - Short History of Modern Philosophy §11.7 | |
| A reaction: The trouble with these transcendental arguments of Kant is that they render you powerless to discuss the question of whether values are actually objective. We are all trapped in presuppositions, instead of testing suppositions. |
| 20410 | The judgement of beauty is not cognitive, but relates, via imagination, to pleasurable feelings [Kant] |
| Full Idea: In order to understand whether or not something is beautiful, we do not relate the representation by means of understanding to the object for cognition, but relate it by means of the imagination ..to the subject and its feeling of pleasure or displeasure. | |
| From: Immanuel Kant (Critique of Judgement I: Aesthetic [1790], CUP 1 5:203), quoted by Elizabeth Schellekens - Immanuel Kant (aesthetics) 2.1 | |
| A reaction: This is to distinguish the particular type of judgement which counts as 'aesthetic' - the point being that it is not cognitive - it is not a matter of knowledge and facts, but a cool judgement made about a warm feeling of pleasure. I think. |
| 16713 | Philosophers are the forefathers of heretics [Tertullian] |
| Full Idea: Philosophers are the forefathers of heretics. | |
| From: Tertullian (works [c.200]), quoted by Robert Pasnau - Metaphysical Themes 1274-1671 20.2 |
| 6610 | I believe because it is absurd [Tertullian] |
| Full Idea: I believe because it is absurd ('Credo quia absurdum est'). | |
| From: Tertullian (works [c.200]), quoted by Robert Fogelin - Walking the Tightrope of Reason n4.2 | |
| A reaction: This seems to be a rather desperate remark, in response to what must have been rather good hostile arguments. No one would abandon the support of reason if it was easy to acquire. You can't deny its engaging romantic defiance, though. |