23 ideas
| 8623 | Proof reveals the interdependence of truths, as well as showing their certainty [Euclid, by Frege] |
| Full Idea: Euclid gives proofs of many things which anyone would concede to him without question. ...The aim of proof is not merely to place the truth of a proposition beyond doubt, but also to afford us insight into the dependence of truths upon one another. | |
| From: report of Euclid (Elements of Geometry [c.290 BCE]) by Gottlob Frege - Grundlagen der Arithmetik (Foundations) §02 | |
| A reaction: This connects nicely with Shoemaker's view of analysis (Idea 8559), which I will adopt as my general view. I've always thought of philosophy as the aspiration to wisdom through the cartography of concepts. |
| 13907 | If you pick an arbitrary triangle, things proved of it are true of all triangles [Euclid, by Lemmon] |
| Full Idea: Euclid begins proofs about all triangles with 'let ABC be a triangle', but ABC is not a proper name. It names an arbitrarily selected triangle, and if that has a property, then we can conclude that all triangles have the property. | |
| From: report of Euclid (Elements of Geometry [c.290 BCE]) by E.J. Lemmon - Beginning Logic 3.2 | |
| A reaction: Lemmon adds the proviso that there must be no hidden assumptions about the triangle we have selected. You must generalise the properties too. Pick a triangle, any triangle, say one with three angles of 60 degrees; now generalise from it. |
| 12797 | If plural variables have 'some values', then non-count variables have 'some value' [Laycock] |
| Full Idea: If a plural variable is said to have not a single value but some values (some clothes), then a non-count variable may have, more quirkier still, some value (some clothing, for instance) in ranging arbitrarily over the scattered stuff. | |
| From: Henry Laycock (Words without Objects [2006], 4.4) | |
| A reaction: We seem to need the notion of a sample, or an archetype, to fit the bill. I hereby name them 'sample variables'. Damn - Laycock got there first, on p.137. |
| 12794 | Plurals are semantical but not ontological [Laycock] |
| Full Idea: Plurality is a semantical but not also an ontological construction. | |
| From: Henry Laycock (Words without Objects [2006], Intro 4) | |
| A reaction: I love it when philososphers make simple and illuminating remarks like this. You could read 500 pages of technical verbiage about plural reference without grasping that this is the underlying issue. Sounds right to me. |
| 6297 | Euclid's geometry is synthetic, but Descartes produced an analytic version of it [Euclid, by Resnik] |
| Full Idea: Euclid's geometry is a synthetic geometry; Descartes supplied an analytic version of Euclid's geometry, and we now have analytic versions of the early non-Euclidean geometries. | |
| From: report of Euclid (Elements of Geometry [c.290 BCE]) by Michael D. Resnik - Maths as a Science of Patterns One.4 | |
| A reaction: I take it that the original Euclidean axioms were observations about the nature of space, but Descartes turned them into a set of pure interlocking definitions which could still function if space ceased to exist. |
| 9603 | An assumption that there is a largest prime leads to a contradiction [Euclid, by Brown,JR] |
| Full Idea: Assume a largest prime, then multiply the primes together and add one. The new number isn't prime, because we assumed a largest prime; but it can't be divided by a prime, because the remainder is one. So only a larger prime could divide it. Contradiction. | |
| From: report of Euclid (Elements of Geometry [c.290 BCE]) by James Robert Brown - Philosophy of Mathematics Ch.1 | |
| A reaction: Not only a very elegant mathematical argument, but a model for how much modern logic proceeds, by assuming that the proposition is false, and then deducing a contradiction from it. |
| 9894 | A unit is that according to which each existing thing is said to be one [Euclid] |
| Full Idea: A unit is that according to which each existing thing is said to be one. | |
| From: Euclid (Elements of Geometry [c.290 BCE], 7 Def 1) | |
| A reaction: See Frege's 'Grundlagen' §29-44 for a sustained critique of this. Frege is good, but there must be something right about the Euclid idea. If I count stone, paper and scissors as three, each must first qualify to be counted as one. Psychology creeps in. |
| 17694 | Some non-count nouns can be used for counting, as in 'several wines' or 'fewer cheeses' [Laycock] |
| Full Idea: The very words we class as non-count nouns may themselves be used for counting, of kinds or types, and phrases like 'several wines' are perfectly in order. ...Not only do we have 'less cheese', but we also have the non-generic 'fewer cheeses'. | |
| From: Henry Laycock (Words without Objects [2006], Intro 4 n23) | |
| A reaction: [compressed] Laycock generally endorses the thought that what can be counted is not simply distinguished by a precise class of applied vocabulary. He offers lots of borderline or ambiguous cases in his footnotes. |
| 17695 | Some apparent non-count words can take plural forms, such as 'snows' or 'waters' [Laycock] |
| Full Idea: Some words that seem to be semantically non-count can take syntactically plural forms: 'snows', 'sands', 'waters' and the like. | |
| From: Henry Laycock (Words without Objects [2006], Intro 4 n24) | |
| A reaction: This seems to involve parcels of the stuff. The 'snows of yesteryear' occur at different times. 'Taking the waters' probably involves occasions. The 'Arabian sands' presumably occur in different areas. Semantics won't fix what is countable. |
| 8738 | Postulate 2 says a line can be extended continuously [Euclid, by Shapiro] |
| Full Idea: Euclid's Postulate 2 says the geometer can 'produce a finite straight line continuously in a straight line'. | |
| From: report of Euclid (Elements of Geometry [c.290 BCE]) by Stewart Shapiro - Thinking About Mathematics 4.2 | |
| A reaction: The point being that this takes infinity for granted, especially if you start counting how many points there are on the line. The Einstein idea that it might eventually come round and hit you on the back of the head would have charmed Euclid. |
| 10302 | Euclid says we can 'join' two points, but Hilbert says the straight line 'exists' [Euclid, by Bernays] |
| Full Idea: Euclid postulates: One can join two points by a straight line; Hilbert states the axiom: Given any two points, there exists a straight line on which both are situated. | |
| From: report of Euclid (Elements of Geometry [c.290 BCE]) by Paul Bernays - On Platonism in Mathematics p.259 |
| 22278 | Euclid relied on obvious properties in diagrams, as well as on his axioms [Potter on Euclid] |
| Full Idea: Euclid's axioms were insufficient to derive all the theorems of geometry: at various points in his proofs he appealed to properties that are obvious from the diagrams but do not follow from the stated axioms. | |
| From: comment on Euclid (Elements of Geometry [c.290 BCE]) by Michael Potter - The Rise of Analytic Philosophy 1879-1930 03 'aim' | |
| A reaction: I suppose if the axioms of a system are based on self-evidence, this would licence an appeal to self-evidence elsewhere in the system. Only pedants insist on writing down what is obvious to everyone! |
| 8673 | Euclid's parallel postulate defines unique non-intersecting parallel lines [Euclid, by Friend] |
| Full Idea: Euclid's fifth 'parallel' postulate says if there is an infinite straight line and a point, then there is only one straight line through the point which won't intersect the first line. This axiom is independent of Euclid's first four (agreed) axioms. | |
| From: report of Euclid (Elements of Geometry [c.290 BCE]) by Michèle Friend - Introducing the Philosophy of Mathematics 2.2 | |
| A reaction: This postulate was challenged in the nineteenth century, which was a major landmark in the development of modern relativist views of knowledge. |
| 10250 | Euclid needs a principle of continuity, saying some lines must intersect [Shapiro on Euclid] |
| Full Idea: Euclid gives no principle of continuity, which would sanction an inference that if a line goes from the outside of a circle to the inside of circle, then it must intersect the circle at some point. | |
| From: comment on Euclid (Elements of Geometry [c.290 BCE]) by Stewart Shapiro - Philosophy of Mathematics 6.1 n2 | |
| A reaction: Cantor and Dedekind began to contemplate discontinuous lines. |
| 14157 | Modern geometries only accept various parts of the Euclid propositions [Russell on Euclid] |
| Full Idea: In descriptive geometry the first 26 propositions of Euclid hold. In projective geometry the 1st, 7th, 16th and 17th require modification (as a straight line is not a closed series). Those after 26 depend on the postulate of parallels, so aren't assumed. | |
| From: comment on Euclid (Elements of Geometry [c.290 BCE]) by Bertrand Russell - The Principles of Mathematics §388 |
| 1600 | Euclid's common notions or axioms are what we must have if we are to learn anything at all [Euclid, by Roochnik] |
| Full Idea: The best known example of Euclid's 'common notions' is "If equals are subtracted from equals the remainders are equal". These can be called axioms, and are what "the man who is to learn anything whatever must have". | |
| From: report of Euclid (Elements of Geometry [c.290 BCE], 72a17) by David Roochnik - The Tragedy of Reason p.149 |
| 12792 | The category of stuff does not suit reference [Laycock] |
| Full Idea: The central fact about the category of stuff or matter is that it is profoundly antithetical to reference. | |
| From: Henry Laycock (Words without Objects [2006], Pref) | |
| A reaction: This is taking 'reference' in the strictly singular classical sense, but clearly we refer to water in various ways. Laycock's challenge is very helpful. We have been in the grips of a terrible orthodoxy. |
| 12799 | Descriptions of stuff are neither singular aggregates nor plural collections [Laycock] |
| Full Idea: The definite descriptions of stuff like water are neither singular descriptions denoting individual mereological aggregates, nor plural descriptions denoting multitudes of discrete units or semantically determined atoms. | |
| From: Henry Laycock (Words without Objects [2006], 5.3) | |
| A reaction: Laycock makes an excellent case for this claim, and seems to invite a considerable rethink of our basic ontology to match it, one which he ultimately hints at calling 'romantic'. Nice. Conservatives try to force stuff into classical moulds. |
| 12818 | We shouldn't think some water retains its identity when it is mixed with air [Laycock] |
| Full Idea: Suppose that water, qua vapour, mixes with the atmosphere. Is there any abstract metaphysical principle, other than that of atomism, which implies that water must, in any such process, retain its identity? That claim seems indefensible. | |
| From: Henry Laycock (Words without Objects [2006], 1.2 n22) | |
| A reaction: It can't be right that some stuff always loses its identity in a mixture, if the mixture was in a closed vessel, and then separated again. Dispersion is what destroys the identity, not mixing. |
| 12795 | Parts must be of the same very general type as the wholes [Laycock] |
| Full Idea: The notion of a part is such that parts must be of the same very general type - concrete, material or physical, for instance - as the wholes of which they are (said to be) parts. | |
| From: Henry Laycock (Words without Objects [2006], 2.9) | |
| A reaction: The phrase 'same very general type' cries out for investigation. Can an army contain someone who isn't much of a soldier? Can the Treasury contain a fear of inflation? |
| 604 | Knowledge is mind and knowing 'cohabiting' [Lycophron, by Aristotle] |
| Full Idea: Lycophron has it that knowledge is the 'cohabitation' (rather than participation or synthesis) of knowing and the soul. | |
| From: report of Lycophron (fragments/reports [c.375 BCE]) by Aristotle - Metaphysics 1045b | |
| A reaction: This sounds like a rather passive and inert relationship. Presumably knowing something implies the possibility of acting on it. |
| 17696 | 'Humility is a virtue' has an abstract noun, but 'water is a liquid' has a generic concrete noun [Laycock] |
| Full Idea: Work is needed to distinguish abstract nouns ...from the generic uses of what are otherwise concrete nouns. The contrast is that of 'humility is a virtue' and 'water is a liquid'. | |
| From: Henry Laycock (Words without Objects [2006], Intro 4 n25) | |
| A reaction: 'Work is needed' implies 'let me through, I'm an analytic philosopher', but I don't think they will separate very easily. What does 'watery' mean? Does water have concrete virtues? |
| 12791 | It is said that proper reference is our intellectual link with the world [Laycock] |
| Full Idea: Some people hold that it is reference, in some more or less full-blooded sense, which constitutes our basic intellectual or psychological connection with the world. | |
| From: Henry Laycock (Words without Objects [2006], Pref) | |
| A reaction: This is the view which Laycock sets out to challenge, by showing that we talk about stuff like water without any singular reference occurring at all. I think he is probably right. |