44 ideas
| 23889 | Among the Greeks Aristotle is the only philosopher in the modern style [Weil] |
| Full Idea: In Greece, Aristotle is perhaps the only philosopher in the modern sense, and he is entirely outside the Greek tradition. | |
| From: Simone Weil (God in Plato [1942], p.45) | |
| A reaction: She sees Plato as embodying the true tradition. Everything Aristotle writes is 'peri phusis' (about nature), and that is a standard topic of philosophy right from the start. She emphasises Plato long historical roots. Pythagoras is key. |
| 21955 | My dogmatic slumber was first interrupted by David Hume [Kant] |
| Full Idea: I freely admit that remembrance of David Hume was the very thing that many years ago first interrupted my dogmatic slumber. | |
| From: Immanuel Kant (Prolegomena to Any Future Metaphysic [1781], 4:260), quoted by A.W. Moore - The Evolution of Modern Metaphysics 5.2 | |
| A reaction: A famous declaration. He realised that he had the answer the many scepticisms of Hume, and accept his emphasis on the need for experience. |
| 16931 | Metaphysics is generating a priori knowledge by intuition and concepts, leading to the synthetic [Kant] |
| Full Idea: The generation of knowledge a priori, both according to intuition and according to concepts, and finally the generation of synthetic propositions a priori in philosophical knowledge, constitutes the essential content of metaphysics. | |
| From: Immanuel Kant (Prolegomena to Any Future Metaphysic [1781], 274) | |
| A reaction: By 'concepts' he implies mere analytic thought, so 'intuition' is where the exciting bit is, and that is rather vague. |
| 8729 | Intuitionists deny excluded middle, because it is committed to transcendent truth or objects [Shapiro] |
| Full Idea: Intuitionists in mathematics deny excluded middle, because it is symptomatic of faith in the transcendent existence of mathematical objects and/or the truth of mathematical statements. | |
| From: Stewart Shapiro (Thinking About Mathematics [2000], 1.2) | |
| A reaction: There are other problems with excluded middle, such as vagueness, but on the whole I, as a card-carrying 'realist', am committed to the law of excluded middle. |
| 16918 | Mathematics cannot proceed just by the analysis of concepts [Kant] |
| Full Idea: Mathematics cannot proceed analytically, namely by analysis of concepts, but only synthetically. | |
| From: Immanuel Kant (Prolegomena to Any Future Metaphysic [1781], 284) | |
| A reaction: I'm with Kant insofar as I take mathematics to be about the world, no matter how rarefied and 'abstract' it may become. |
| 16930 | Geometry is not analytic, because a line's being 'straight' is a quality [Kant] |
| Full Idea: No principle of pure geometry is analytic. That the straight line beween two points is the shortest is a synthetic proposition. For my concept of straight contains nothing of quantity but only of quality. | |
| From: Immanuel Kant (Prolegomena to Any Future Metaphysic [1781], 269) | |
| A reaction: I'm not sure what his authority is for calling straightness a quality rather than a quantity, given that it can be expressed quantitatively. It is a very nice example for focusing our questions about the nature of geometry. I can't decide. |
| 16919 | Geometry rests on our intuition of space [Kant] |
| Full Idea: Geometry is grounded on the pure intuition of space. | |
| From: Immanuel Kant (Prolegomena to Any Future Metaphysic [1781], 284) | |
| A reaction: I have the impression that recent thinkers are coming round to this idea, having attempted purely algebraic or logical accounts of geometry. |
| 16920 | Numbers are formed by addition of units in time [Kant] |
| Full Idea: Arithmetic forms its own concepts of numbers by successive addition of units in time. | |
| From: Immanuel Kant (Prolegomena to Any Future Metaphysic [1781], 284) | |
| A reaction: It is hard to imagine any modern philosopher of mathematics embracing this idea. It sounds as if Kant thinks counting is the foundation of arithmetic, which I quite like. |
| 8763 | The number 3 is presumably identical as a natural, an integer, a rational, a real, and complex [Shapiro] |
| Full Idea: It is surely wise to identify the positions in the natural numbers structure with their counterparts in the integer, rational, real and complex number structures. | |
| From: Stewart Shapiro (Thinking About Mathematics [2000], 10.2) | |
| A reaction: The point is that this might be denied, since 3, 3/1, 3.00.., and -3*i^2 are all arrived at by different methods of construction. Natural 3 has a predecessor, but real 3 doesn't. I agree, intuitively, with Shapiro. Russell (1919) disagreed. |
| 18249 | Cauchy gave a formal definition of a converging sequence. [Shapiro] |
| Full Idea: A sequence a1,a2,... of rational numbers is 'Cauchy' if for each rational number ε>0 there is a natural number N such that for all natural numbers m, n, if m>N and n>N then -ε < am - an < ε. | |
| From: Stewart Shapiro (Thinking About Mathematics [2000], 7.2 n4) | |
| A reaction: The sequence is 'Cauchy' if N exists. |
| 16929 | 7+5 = 12 is not analytic, because no analysis of 7+5 will reveal the concept of 12 [Kant] |
| Full Idea: The concept of twelve is in no way already thought by merely thinking the unification of seven and five, and though I analyse my concept of such a possible sum as long as I please, I shall never find twelve in it. | |
| From: Immanuel Kant (Prolegomena to Any Future Metaphysic [1781], 269) | |
| A reaction: It might be more plausible to claim that an analysis of 12 would reveal the concept of 7+5. Doesn't the concept of two collections of objects contain the concept of their combined cardinality? |
| 8764 | Categories are the best foundation for mathematics [Shapiro] |
| Full Idea: There is a dedicated contingent who hold that the category of 'categories' is the proper foundation for mathematics. | |
| From: Stewart Shapiro (Thinking About Mathematics [2000], 10.3 n7) | |
| A reaction: He cites Lawvere (1966) and McLarty (1993), the latter presenting the view as a form of structuralism. I would say that the concept of a category will need further explication, and probably reduce to either sets or relations or properties. |
| 8762 | Two definitions of 3 in terms of sets disagree over whether 1 is a member of 3 [Shapiro] |
| Full Idea: Zermelo said that for each number n, its successor is the singleton of n, so 3 is {{{null}}}, and 1 is not a member of 3. Von Neumann said each number n is the set of numbers less than n, so 3 is {null,{null},{null,{null}}}, and 1 is a member of 3. | |
| From: Stewart Shapiro (Thinking About Mathematics [2000], 10.2) | |
| A reaction: See Idea 645 - Zermelo could save Plato from the criticisms of Aristotle! These two accounts are cited by opponents of the set-theoretical account of numbers, because it seems impossible to arbitrate between them. |
| 8760 | Numbers do not exist independently; the essence of a number is its relations to other numbers [Shapiro] |
| Full Idea: The structuralist vigorously rejects any sort of ontological independence among the natural numbers; the essence of a natural number is its relations to other natural numbers. | |
| From: Stewart Shapiro (Thinking About Mathematics [2000], 10.1) | |
| A reaction: This seems to place the emphasis on ordinals (what order?) rather than on cardinality (how many?). I am strongly inclined to think that this is the correct view, though you can't really have relations if there is nothing to relate. |
| 8761 | A 'system' is related objects; a 'pattern' or 'structure' abstracts the pure relations from them [Shapiro] |
| Full Idea: A 'system' is a collection of objects with certain relations among them; a 'pattern' or 'structure' is the abstract form of a system, highlighting the interrelationships and ignoring any features they do not affect how they relate to other objects. | |
| From: Stewart Shapiro (Thinking About Mathematics [2000], 10.1) | |
| A reaction: Note that 'ignoring' features is a psychological account of abstraction, which (thanks to Frege and Geach) is supposed to be taboo - but which I suspect is actually indispensable in any proper account of thought and concepts. |
| 16910 | Mathematics can only start from an a priori intuition which is not empirical but pure [Kant] |
| Full Idea: We find that all mathematical knowledge has this peculiarity, that it must first exhibit its concept in intuition, and do so a priori, in an intuition that is not empirical but pure. | |
| From: Immanuel Kant (Prolegomena to Any Future Metaphysic [1781], 281) | |
| A reaction: Later thinkers had grave doubts about this Kantian 'intuition', even if they though maths was known a priori. Personally I am increasing fan of rational intuition, even if I am not sure how to discern whether it is rational on any occasion. |
| 16917 | All necessary mathematical judgements are based on intuitions of space and time [Kant] |
| Full Idea: Space and time are the two intuitions on which pure mathematics grounds all its cognitions and judgements that present themselves as at once apodictic and necessary. | |
| From: Immanuel Kant (Prolegomena to Any Future Metaphysic [1781], 284) | |
| A reaction: This unlikely proposal seems to be based on the idea that mathematics must arise from the basic categories of our intuition, and these two are the best candidates he can find. I would say that high-level generality is the basis of mathematics. |
| 16928 | Mathematics cannot be empirical because it is necessary, and that has to be a priori [Kant] |
| Full Idea: Mathematical propositions are always judgements a priori, and not empirical, because they carry with them necessity, which cannot be taken from experience. | |
| From: Immanuel Kant (Prolegomena to Any Future Metaphysic [1781], 268) | |
| A reaction: Presumably there are necessities in the physical world, and we might discern them by generalising about that world, so that mathematics is (by a tortuous abstract route) a posteriori necessary? Just a thought… |
| 8744 | Logicism seems to be a non-starter if (as is widely held) logic has no ontology of its own [Shapiro] |
| Full Idea: The thesis that principles of arithmetic are derivable from the laws of logic runs against a now common view that logic itself has no ontology. There are no particular logical objects. From this perspective logicism is a non-starter. | |
| From: Stewart Shapiro (Thinking About Mathematics [2000], 5.1) | |
| A reaction: This criticism strikes me as utterly devastating. There are two routes to go: prove that logic does have an ontology of objects (what would they be?), or - better - deny that arithmetic contains any 'objects'. Or give up logicism. |
| 8749 | Term Formalism says mathematics is just about symbols - but real numbers have no names [Shapiro] |
| Full Idea: Term Formalism is the view that mathematics is just about characters or symbols - the systems of numerals and other linguistic forms. ...This will cover integers and rational numbers, but what are real numbers supposed to be, if they lack names? | |
| From: Stewart Shapiro (Thinking About Mathematics [2000], 6.1.1) | |
| A reaction: Real numbers (such as pi and root-2) have infinite decimal expansions, so we can start naming those. We could also start giving names like 'Harry' to other reals, though it might take a while. OK, I give up. |
| 8750 | Game Formalism is just a matter of rules, like chess - but then why is it useful in science? [Shapiro] |
| Full Idea: Game Formalism likens mathematics to chess, where the 'content' of mathematics is exhausted by the rules of operating with its language. ...This, however, leaves the problem of why the mathematical games are so useful to the sciences. | |
| From: Stewart Shapiro (Thinking About Mathematics [2000], 6.1.2) | |
| A reaction: This thought pushes us towards structuralism. It could still be a game, but one we learned from observing nature, which plays its own games. Chess is, after all, modelled on warfare. |
| 8752 | Deductivism says mathematics is logical consequences of uninterpreted axioms [Shapiro] |
| Full Idea: The Deductivist version of formalism (sometimes called 'if-thenism') says that the practice of mathematics consists of determining logical consequences of otherwise uninterpreted axioms. | |
| From: Stewart Shapiro (Thinking About Mathematics [2000], 6.2) | |
| A reaction: [Hilbert is the source] More plausible than Term or Game Formalism (qv). It still leaves the question of why it seems applicable to nature, and why those particular axioms might be chosen. In some sense, though, it is obviously right. |
| 8753 | Critics resent the way intuitionism cripples mathematics, but it allows new important distinctions [Shapiro] |
| Full Idea: Critics commonly complain that the intuitionist restrictions cripple the mathematician. On the other hand, intuitionist mathematics allows for many potentially important distinctions not available in classical mathematics, and is often more subtle. | |
| From: Stewart Shapiro (Thinking About Mathematics [2000], 7.1) | |
| A reaction: The main way in which it cripples is its restriction on talk of infinity ('Cantor's heaven'), which was resented by Hilbert. Since high-level infinities are interesting, it would be odd if we were not allowed to discuss them. |
| 8731 | Conceptualist are just realists or idealist or nominalists, depending on their view of concepts [Shapiro] |
| Full Idea: I classify conceptualists according to what they say about properties or concepts. If someone classified properties as existing independent of language I would classify her as a realist in ontology of mathematics. Or they may be idealists or nominalists. | |
| From: Stewart Shapiro (Thinking About Mathematics [2000], 2.2.1) | |
| A reaction: In other words, Shapiro wants to eliminate 'conceptualist' as a useful label in philosophy of mathematics. He's probably right. All thought involves concepts, but that doesn't produce a conceptualist theory of, say, football. |
| 8730 | 'Impredicative' definitions refer to the thing being described [Shapiro] |
| Full Idea: A definition of a mathematical entity is 'impredicative' if it refers to a collection that contains the defined entity. The definition of 'least upper bound' is impredicative as it refers to upper bounds and characterizes a member of this set. | |
| From: Stewart Shapiro (Thinking About Mathematics [2000], 1.2) | |
| A reaction: The big question is whether mathematics can live with impredicative definitions, or whether they threaten to be viciously circular, and undermine the whole enterprise. |
| 11833 | The substance, once the predicates are removed, remains unknown to us [Kant] |
| Full Idea: It has long since been noticed that in all substances the subject proper, namely what is left over after all the accidents (as predicates) have been taken away and hence the 'substantial' itself, is unknown to us. | |
| From: Immanuel Kant (Prolegomena to Any Future Metaphysic [1781], 333) | |
| A reaction: This is the terminus of the process of abstraction (though Wiggins says such removal of predicates is a myth). Kant is facing the problem of the bare substratum, or haecceity. |
| 21957 | 'Transcendental' concerns how we know, rather than what we know [Kant] |
| Full Idea: The word 'transcendental' signifies not a relation of our cognition to things, but only to the faculty of cognition. | |
| From: Immanuel Kant (Prolegomena to Any Future Metaphysic [1781], 4:293), quoted by A.W. Moore - The Evolution of Modern Metaphysics 5.4 | |
| A reaction: This is the annoying abduction of a word which is very useful in metaphysical contexts. |
| 16923 | I admit there are bodies outside us [Kant] |
| Full Idea: I do indeed admit that there are bodies outside us. | |
| From: Immanuel Kant (Prolegomena to Any Future Metaphysic [1781], 289 n.II) | |
| A reaction: This is the end of a passage in which Kant very explicitly denies being an idealist. Of course, he says we can only know the representations of things, and not how they are in themselves. |
| 21441 | 'Transcendental' is not beyond experience, but a prerequisite of experience [Kant] |
| Full Idea: The word 'transcendental' does not mean something that goes beyond all experience, but something which, though it precedes (a priori) all experience, is destined only to make knowledge by experience possible. | |
| From: Immanuel Kant (Prolegomena to Any Future Metaphysic [1781], 373 n) | |
| A reaction: One of two explanations by Kant of 'transcendental', picked out by Sebastian Gardner. I think the word 'prerequisite' covers the idea nicely, using a normal English word. Or am I missing something? |
| 16916 | A priori synthetic knowledge is only of appearances, not of things in themselves [Kant] |
| Full Idea: Through intuition we can only know objects as they appear to us (to our senses), not as they may be in themselves; and this presupposition is absolutely necessary if synthetic propositions a priori are to be granted as possible. | |
| From: Immanuel Kant (Prolegomena to Any Future Metaphysic [1781], 283) | |
| A reaction: This idea is basic to understanding Kant, and especially his claim that arithmetic is a priori synthetic. |
| 16915 | A priori intuitions can only concern the objects of our senses [Kant] |
| Full Idea: Intuitions which are possible a priori can never concern any other things than objects of our senses. | |
| From: Immanuel Kant (Prolegomena to Any Future Metaphysic [1781], 283) | |
| A reaction: Given the Kantian idea that what is known a priori will also be necessary, we might have had great hopes for big-time metaphysics, but this idea cuts it down to size. Personally, I don't think we are totally imprisoned in the phenomena. |
| 16914 | A priori intuition of objects is only possible by containing the form of my sensibility [Kant] |
| Full Idea: The only way for my intuition to precede the reality of the object and take place as knowledge a priori is if it contains nothing else than the form of sensibility which in me as subject precedes all real impressions through which I'm affected by objects. | |
| From: Immanuel Kant (Prolegomena to Any Future Metaphysic [1781], 283) | |
| A reaction: This may be the single most famous idea in Kant. I'm not really a Kantian, but this is a powerful idea, the culmination of Descartes' proposal to start philosophy by looking at ourselves. No subsequent thinking can ignore the idea. |
| 21447 | I can make no sense of the red experience being similar to the quality in the object [Kant] |
| Full Idea: I can make little sense of the assertion that the sensation of red is similar to the property of the vermilion [cinnabar] which excites this sensation in me. | |
| From: Immanuel Kant (Prolegomena to Any Future Metaphysic [1781], 290) | |
| A reaction: A sensible remark. In Kant's case it is probably a part of his scepticism that his intuitions reveal anything directly about reality. Locke seems to have thought (reasonably enough) that the experience contains some sort of valid information. |
| 16924 | I count the primary features of things (as well as the secondary ones) as mere appearances [Kant] |
| Full Idea: I also count as mere appearances, in addition to [heat, colour, taste], the remaining qualities of bodies which are called primariae, extension, place, and space in general, with all that depends on it (impenetrability or materiality, shape etc.). | |
| From: Immanuel Kant (Prolegomena to Any Future Metaphysic [1781], 289 n.II) | |
| A reaction: He sides with Berkeley and Hume against Locke and Boyle. He denies being an idealist (Idea 16923), so it seems to me that Kant might be described as a 'phenomenalist'. |
| 16913 | I can't intuit a present thing in itself, because the properties can't enter my representations [Kant] |
| Full Idea: It seems inconceivable how the intuition of a thing that is present should make me know it as it is in itself, for its properties cannot migrate into my faculty of representation. | |
| From: Immanuel Kant (Prolegomena to Any Future Metaphysic [1781], 282) | |
| A reaction: One might compare this with Locke's distinction of primary and secondary, where the primary properties seem to 'migrate into my faculty of representation', but the secondary ones fail to do so. I think I prefer Locke. This idea threatens idealism. |
| 8725 | Rationalism tries to apply mathematical methodology to all of knowledge [Shapiro] |
| Full Idea: Rationalism is a long-standing school that can be characterized as an attempt to extend the perceived methodology of mathematics to all of knowledge. | |
| From: Stewart Shapiro (Thinking About Mathematics [2000], 1.1) | |
| A reaction: Sometimes called 'Descartes's Dream', or the 'Enlightenment Project', the dream of proving everything. Within maths, Hilbert's Programme aimed for the same certainty. Idea 22 is the motto for the opposition to this approach. |
| 16925 | Appearance gives truth, as long as it is only used within experience [Kant] |
| Full Idea: Appearance brings forth truth so long as it is used in experience, but as soon as it goes beyond the boundary of experience and becomes transcendent, it brings forth nothing but illusion. | |
| From: Immanuel Kant (Prolegomena to Any Future Metaphysic [1781], 292 n.III) | |
| A reaction: This is the nearest I have found to Kant declaring for empiricism. It sounds something like direct realism, if experience itself can bring forth truth. |
| 16911 | Intuition is a representation that depends on the presence of the object [Kant] |
| Full Idea: Intuition is a representation, such as would depend on the presence of the object. | |
| From: Immanuel Kant (Prolegomena to Any Future Metaphysic [1781], 282) | |
| A reaction: This is a distinctively Kantian view of intuition, which arises through particulars, rather than the direct apprehension of generalities. |
| 16912 | Some concepts can be made a priori, which are general thoughts of objects, like quantity or cause [Kant] |
| Full Idea: Concepts are of such a nature that we can make some of them ourselves a priori, without standing in any immediate relation to the object; namely concepts that contain the thought of an object in general, such as quantity or cause. | |
| From: Immanuel Kant (Prolegomena to Any Future Metaphysic [1781], 282) | |
| A reaction: 'Quantity' seems to be the scholastic idea, of something having a magnitude (a big pebble, not six pebbles). |
| 16926 | Analytic judgements say clearly what was in the concept of the subject [Kant] |
| Full Idea: Analytic judgements say nothing in the predicate that was not already thought in the concept of the subject, though not so clearly and with the same consciousness. If I say all bodies are extended, I have not amplified my concept of body in the least. | |
| From: Immanuel Kant (Prolegomena to Any Future Metaphysic [1781], 266) | |
| A reaction: If I say all bodies are made of atoms, have I extended my concept of 'body'? It would come as a sensational revelation for Aristotle, but it now seems analytic. |
| 16927 | Analytic judgement rests on contradiction, since the predicate cannot be denied of the subject [Kant] |
| Full Idea: Analytic judgements rest wholly on the principle of contradiction, …because the predicate cannot be denied of the subject without contradiction. | |
| From: Immanuel Kant (Prolegomena to Any Future Metaphysic [1781], 267) | |
| A reaction: So if I say 'gold has atomic number 79', that is a (Kantian) analytic statement? This is the view of sceptics about Kripke's a posteriori necessity. …a few lines later Kant gives 'gold is a yellow metal' as an example. |
| 16922 | Space must have three dimensions, because only three lines can meet at right angles [Kant] |
| Full Idea: That complete space …has three dimensions, and that space in general cannot have more, is built on the proposition that not more than three lines can intersect at right angles in a point. | |
| From: Immanuel Kant (Prolegomena to Any Future Metaphysic [1781], 285) | |
| A reaction: Modern geometry seems to move, via the algebra, to more than three dimensions, and then battles for an intuition of how that can be. I don't know how they would respond to Kant's challenge here. |
| 16921 | If all empirical sensation of bodies is removed, space and time are still left [Kant] |
| Full Idea: If everything empirical, namely what belongs to sensation, is taken away from the empirical intuition of bodies and their changes (motion), space and time are still left. | |
| From: Immanuel Kant (Prolegomena to Any Future Metaphysic [1781], 284) | |
| A reaction: This is an exercise in psychological abstraction, which doesn't sound like good evidence, though it is an interesting claim. Physicists want to hijack this debate, but I like Kant's idea. |
| 23892 | The only legitimate proof of God by order derives from beauty [Weil] |
| Full Idea: The only legitimate proof [of God's existence] from the order of the world is the proof from the beauty of the world. | |
| From: Simone Weil (God in Plato [1942], p.89) | |
| A reaction: She finds this proof in Plato. Hume's critique never (I think) mentions beauty, although in the 18thC love of the sublime could play that role. For me, the human experience of beauty doesn't have such cosmic significance. |