102 ideas
| 11006 | Russell started a whole movement in philosophy by providing an analysis of descriptions [Read on Russell] |
| Full Idea: Russell started a whole movement in philosophy by providing an analysis of descriptions. | |
| From: comment on Bertrand Russell (On Denoting [1905]) by Stephen Read - Thinking About Logic Ch.5 |
| 4901 | Truth has to be correspondence to facts, and a match between relations of ideas and relations in the world [Perry] |
| Full Idea: I think knowledge and truth are a matter of correspondence to facts, despite all the energy spent showing the naïveté of this view. The connections of our ideas in our heads correspond to relations in the outside world. | |
| From: John Perry (Knowledge, Possibility and Consciousness [2001], §8.1) | |
| A reaction: Yes. Modern books offer the difficulties of defining 'correspondence', and finding an independent account of 'facts', as conclusive objections, but I say a brain is a truth machine, and it had better be useful. Indefinability doesn't nullify concepts. |
| 15901 | Trying to represent curves, we study arbitrary functions, leading to the ordinals, which produces set theory [Cantor, by Lavine] |
| Full Idea: The notion of a function evolved gradually from wanting to see what curves can be represented as trigonometric series. The study of arbitrary functions led Cantor to the ordinal numbers, which led to set theory. | |
| From: report of George Cantor (works [1880]) by Shaughan Lavine - Understanding the Infinite I |
| 13444 | Cantor's Theorem: for any set x, its power set P(x) has more members than x [Cantor, by Hart,WD] |
| Full Idea: Cantor's Theorem says that for any set x, its power set P(x) has more members than x. | |
| From: report of George Cantor (works [1880]) by William D. Hart - The Evolution of Logic 1 |
| 18098 | Cantor proved that all sets have more subsets than they have members [Cantor, by Bostock] |
| Full Idea: Cantor's diagonalisation argument generalises to show that any set has more subsets than it has members. | |
| From: report of George Cantor (works [1880]) by David Bostock - Philosophy of Mathematics 4.5 | |
| A reaction: Thus three members will generate seven subsets. This means that 'there is no end to the series of cardinal numbers' (Bostock p.106). |
| 15505 | If a set is 'a many thought of as one', beginners should protest against singleton sets [Cantor, by Lewis] |
| Full Idea: Cantor taught that a set is 'a many, which can be thought of as one'. ...After a time the unfortunate beginner student is told that some classes - the singletons - have only a single member. Here is a just cause for student protest, if ever there was one. | |
| From: report of George Cantor (works [1880]) by David Lewis - Parts of Classes 2.1 | |
| A reaction: There is a parallel question, almost lost in the mists of time, of whether 'one' is a number. 'Zero' is obviously dubious, but if numbers are for counting, that needs units, so the unit is the precondition of counting, not part of it. |
| 10701 | Cantor showed that supposed contradictions in infinity were just a lack of clarity [Cantor, by Potter] |
| Full Idea: Cantor's theories exhibited the contradictions others had claimed to derive from the supposition of infinite sets as confusions resulting from the failure to mark the necessary distinctions with sufficient clarity. | |
| From: report of George Cantor (works [1880]) by Michael Potter - Set Theory and Its Philosophy Intro 1 |
| 10865 | The continuum is the powerset of the integers, which moves up a level [Cantor, by Clegg] |
| Full Idea: Cantor discovered that the continuum is the powerset of the integers. While adding or multiplying infinities didn't move up a level of complexity, multiplying a number by itself an infinite number of times did. | |
| From: report of George Cantor (works [1880]) by Brian Clegg - Infinity: Quest to Think the Unthinkable Ch.14 |
| 13016 | The Axiom of Union dates from 1899, and seems fairly obvious [Cantor, by Maddy] |
| Full Idea: Cantor first stated the Union Axiom in a letter to Dedekind in 1899. It is nearly too obvious to deserve comment from most commentators. Justifications usually rest on 'limitation of size' or on the 'iterative conception'. | |
| From: report of George Cantor (works [1880]) by Penelope Maddy - Believing the Axioms I §1.3 | |
| A reaction: Surely someone can think of some way to challenge it! An opportunity to become notorious, and get invited to conferences. |
| 14199 | Cantor's sets were just collections, but Dedekind's were containers [Cantor, by Oliver/Smiley] |
| Full Idea: Cantor's definition of a set was a collection of its members into a whole, but within a few years Dedekind had the idea of a set as a container, enclosing its members like a sack. | |
| From: report of George Cantor (works [1880]) by Oliver,A/Smiley,T - What are Sets and What are they For? Intro | |
| A reaction: As the article goes on to show, these two view don't seem significantly different until you start to ask about the status of the null set and of singletons. I intuitively vote for Dedekind. Set theory is the study of brackets. |
| 18944 | Russell's theories aim to preserve excluded middle (saying all sentences are T or F) [Sawyer on Russell] |
| Full Idea: Russell's account of names and definite descriptions was concerned to preserve the law of excluded middle, according to which every sentence is either true or false (but it is not obvious that the law ought to be preserved). | |
| From: comment on Bertrand Russell (On Denoting [1905]) by Sarah Sawyer - Empty Names 3 | |
| A reaction: That is the strongest form of excluded middle, but things work better if every sentence is either 'true' or 'not true', leaving it open whether 'not true' actually means 'false'. |
| 7758 | 'Elizabeth = Queen of England' is really a predication, not an identity-statement [Russell, by Lycan] |
| Full Idea: On Russell's view 'Elizabeth II = Queen of England' is only superficially an identity-statement; really it is a predication, and attributes a complex relational property to Elizabeth. | |
| From: report of Bertrand Russell (On Denoting [1905]) by William Lycan - Philosophy of Language Ch.1 | |
| A reaction: The original example is 'Scott = author of Waverley'. Why can't such statements be identities, in which the reference of one half of the identity is not yet known? 'The murderer is violent' and 'Smith is violent' suggests 'Smith is the murderer'. |
| 5772 | The idea of a variable is fundamental [Russell] |
| Full Idea: I take the notion of the variable as fundamental. | |
| From: Bertrand Russell (On Denoting [1905], p.42) | |
| A reaction: A key idea of twentieth century philosophy, derived from Frege and handed on to Quine. A universal term, such as 'horse', is a variable, for which any particular horse can be its value. You can calculate using x, and generalise about horses. |
| 18941 | Names don't have a sense, but are disguised definite descriptions [Russell, by Sawyer] |
| Full Idea: Russell proposed that names do not express a Fregean sense, ...but are disguised definite descriptions, of the form 'the F'. | |
| From: report of Bertrand Russell (On Denoting [1905]) by Sarah Sawyer - Empty Names 3 | |
| A reaction: Of course, Russell then has a famous theory about definite descriptions, which turns them into quantifications. |
| 4945 | Russell says names are not denotations, but definite descriptions in disguise [Russell, by Kripke] |
| Full Idea: Russell (and Frege) thought that Mill was wrong about names: really a proper name, properly used, simply was a definite description abbreviated or disguised. | |
| From: report of Bertrand Russell (On Denoting [1905]) by Saul A. Kripke - Naming and Necessity lectures Lecture 1 | |
| A reaction: It is tempting to oversimplify this issue, one way or the other, but essentially one has to agree with Kripke that naming does not inherently involve description, but is a 'baptism', without initial content. Connotations and descriptions accrue to a name. |
| 18942 | Russell says a name contributes a complex of properties, rather than an object [Russell, by Sawyer] |
| Full Idea: Russell's view of names, understood as a definite description, which is understood as a quantificational phrase, is not to contribute an object to propositions, but to contribute a complex of properties. | |
| From: report of Bertrand Russell (On Denoting [1905]) by Sarah Sawyer - Empty Names 3 | |
| A reaction: This seems to contradict the role of constants in first-logic, which are the paradigm names, picking out an object in the domain. Kripke says names and definite descriptions have different modal profiles. |
| 7745 | Are names descriptions, if the description is unknown, false, not special, or contains names? [McCullogh on Russell] |
| Full Idea: Russell's proposal that a natural name is an abbreviated description invites four objections: not all speakers can produce descriptions; the description could be false; no one description seems special; and descriptions usually contain names. | |
| From: comment on Bertrand Russell (On Denoting [1905]) by Gregory McCullogh - The Game of the Name 8.74 | |
| A reaction: The best reply on behalf of Russell is probably to concede all of these points, but deny that any of them are fatal. Most replies will probably say that they are possible true descriptions, rather than actual limited, confused or false ones. |
| 10449 | Logically proper names introduce objects; definite descriptions introduce quantifications [Russell, by Bach] |
| Full Idea: For Russell, a logically proper name introduces its referent into the proposition, whereas a description introduces a certain quantificational structure, not its denotation. | |
| From: report of Bertrand Russell (On Denoting [1905]) by Kent Bach - What Does It Take to Refer? 22.2 L0 | |
| A reaction: I have very strong resistance to the idea that the actual referent could ever become part of a proposition. I am not, and never have been, part of a proposition! Russell depended on narrow 'acquaintance', which meant that few things qualified. |
| 15159 | The meaning of a logically proper name is its referent, but most names are not logically proper [Russell, by Soames] |
| Full Idea: Russell defined a logically proper name to be one the meaning of which is its referent. However, his internalist epistemology led him to deny that the words we ordinarily call names are logically proper. | |
| From: report of Bertrand Russell (On Denoting [1905]) by Scott Soames - Philosophy of Language 1.25 |
| 2612 | Russell rewrote singular term names as predicates [Russell, by Ayer] |
| Full Idea: Russell's theory used quantification to eliminate singular terms, which could be meaningful without denoting anything. He reparsed such sentences so they appeared as predicates instead of names. | |
| From: report of Bertrand Russell (On Denoting [1905]) by A.J. Ayer - The Central Questions of Philosophy IX.A.2 |
| 7757 | "Nobody" is not a singular term, but a quantifier [Russell, by Lycan] |
| Full Idea: Though someone just beginning to learn English might take it as one, "nobody" is not a singular term, but a quantifier. | |
| From: report of Bertrand Russell (On Denoting [1905]) by William Lycan - Philosophy of Language Ch.1 | |
| A reaction: If someone replies to "nobody's there" with "show him to me!", presumably it IS a singular term - just one that doesn't work very well. If you want to get on in life, treat it as a quantifier; if you just want to have fun... |
| 18943 | Russell implies that all sentences containing empty names are false [Sawyer on Russell] |
| Full Idea: Russell's account implies that all sentences composed of an empty name and a predicate are false, including 'Pegasus was a mythical creature'. | |
| From: comment on Bertrand Russell (On Denoting [1905]) by Sarah Sawyer - Empty Names 4 | |
| A reaction: Russell insists that such sentences contain a concealed existence claim, which they clearly don't. |
| 6411 | Critics say definite descriptions can refer, and may not embody both uniqueness and existence claims [Grayling on Russell] |
| Full Idea: The main objections to Russell's theory of descriptions are to say that definite descriptions sometime are referring expressions, and disputing the claim that definite descriptions embody both uniqueness and existence claims. | |
| From: comment on Bertrand Russell (On Denoting [1905]) by A.C. Grayling - Russell Ch.2 | |
| A reaction: The first one seems particularly correct, as you can successfully refer with a false description. See Colin McGinn (Idea 6067) for criticism of the existence claim made by the so-called 'existential' quantifier. |
| 10433 | Definite descriptions fail to refer in three situations, so they aren't essentially referring [Russell, by Sainsbury] |
| Full Idea: Russell's reasons for saying that definite descriptions are not referring expressions are: some definite descriptions have no referent, and they cannot be referring when used in negative existential truths, or in informative identity sentences. | |
| From: report of Bertrand Russell (On Denoting [1905]) by Mark Sainsbury - The Essence of Reference 18.5 | |
| A reaction: The idea is that by 'parity of form', if they aren't referring in these situations, they aren't really referring in others. Sainsbury notes that if there are two different forms of definite description (referential and attributive) these arguments fail. |
| 1608 | The theory of descriptions eliminates the name of the entity whose existence was presupposed [Russell, by Quine] |
| Full Idea: When a statement of being or non-being is analysed by Russell's theory of descriptions it ceases to contain any expression which even purports to name the alleged entity, so the being of such an entity is no longer presupposed. | |
| From: report of Bertrand Russell (On Denoting [1905]) by Willard Quine - On What There Is p.6 |
| 7754 | Russell's theory explains non-existents, negative existentials, identity problems, and substitutivity [Russell, by Lycan] |
| Full Idea: Russell showed that his theory of definite descriptions affords solutions to each of four vexing logical problems: the Problems of Apparent Reference to Non-existents and Negative existentials, Frege's Puzzle about Identity, and Substitutivity. | |
| From: report of Bertrand Russell (On Denoting [1905]) by William Lycan - Philosophy of Language 2.Over | |
| A reaction: You must seek elsewhere for the explanations of the four problems, but this gives some indication of why Russell's theory was famous, and was felt to be a breakthrough in explaining logical forms. |
| 21529 | Russell showed how to define 'the', and thereby reduce the ontology of logic [Russell, by Lackey] |
| Full Idea: With the devices of the Theory of Descriptions at hand, it was no longer necessary to take 'the' as indefinable, and it was possible to diminish greatly the number of entities to which a logical system is ontologically committed. | |
| From: report of Bertrand Russell (On Denoting [1905]) by Douglas Lackey - Intros to Russell's 'Essays in Analysis' p.13 | |
| A reaction: Illuminating, because it shows that ontology is what drove Russell at this time, and really they were all searching for Quine's 'desert landscapes', which minimalise commitment. |
| 6333 | The theory of definite descriptions reduces the definite article 'the' to the concepts of predicate logic [Russell, by Horwich] |
| Full Idea: Russell's theory of definite descriptions reduces the definite article 'the' to the notions of predicate logic - specifically, 'some', 'every', and 'same as'. | |
| From: report of Bertrand Russell (On Denoting [1905]) by Paul Horwich - Truth (2nd edn) Ch.2.7 | |
| A reaction: This helpfully clarifies Russell's project - to find the logical form of every sentence, expressed in terms which are strictly defined and consistent. This huge project now looks rather too optimistic. Artificial Intelligence would love to complete it. |
| 6412 | Russell implies that 'the baby is crying' is only true if the baby is unique [Grayling on Russell] |
| Full Idea: Russell's analysis of 'the baby is crying' seems to imply that this can only be true if there is just one baby in the world; ..to dispose of the objection, it seems necessary to appeal implicitly or explicitly to a 'domain of discourse'. | |
| From: comment on Bertrand Russell (On Denoting [1905]) by A.C. Grayling - Russell Ch.2 | |
| A reaction: This objection leads to ordinary language philosophy, and the 'pragmatics' of language. It is standard in modern predicate logic to specify the domain over which an expression is quantified. |
| 7743 | Russell explained descriptions with quantifiers, where Frege treated them as names [Russell, by McCullogh] |
| Full Idea: Russell proposed that descriptions be treated along with the quantifiers, which departs from Frege, who treated descriptions as proper names. ...the problem was that names invoke objects, and there is no object in failed descriptions. | |
| From: report of Bertrand Russell (On Denoting [1905]) by Gregory McCullogh - The Game of the Name 2.16 | |
| A reaction: Maybe we just allow intentional objects (such as unicorns) into our ontology? Producing a parsimonious ontology seems to be the main motivation of most philosophy of language. Or maybe names are just not committed to actual existence? |
| 7310 | Russell avoids non-existent objects by denying that definite descriptions are proper names [Russell, by Miller,A] |
| Full Idea: Russell attempted to avoid Meinong's strategy (of saying 'The present King of France' refers to a 'non-existent object') by denying that definite descriptions are proper names. | |
| From: report of Bertrand Russell (On Denoting [1905]) by Alexander Miller - Philosophy of Language 2.7 | |
| A reaction: Russell claimed that there was a covert existence claim built into a definite description. What about descriptions in known counterfactual situations ('Queen of the Fairies')? |
| 12006 | Denying definite description sentences are subject-predicate in form blocks two big problems [Russell, by Forbes,G] |
| Full Idea: Since Russell did not want to introduce non-existent objects, or declare many sentences meaningless, he prevented the problem from getting started, by denying that 'the present King of France is bald' is really a subject-predicate sentence. | |
| From: report of Bertrand Russell (On Denoting [1905]) by Graeme Forbes - The Metaphysics of Modality 4.1 |
| 4569 | Russell says apparent referring expressions are really assertions about properties [Russell, by Cooper,DE] |
| Full Idea: Russell's theory says that sentences which apparently serve to refer to particulars are really assertions about properties. | |
| From: report of Bertrand Russell (On Denoting [1905]) by David E. Cooper - Philosophy and the Nature of Language §4.1 | |
| A reaction: Right. Which is why particulars get marginalised in Russell, and universals take centre stage. I can't help suspecting that talk of de re/de dicto reference handles this problem better. |
| 11009 | Russell's theory must be wrong if it says all statements about non-existents are false [Read on Russell] |
| Full Idea: Russell's theory makes an exciting distinction between logical and grammatical form, but any theory which says that every positive statement, without distinction, about objects which don't exist is false, has to be wrong. | |
| From: comment on Bertrand Russell (On Denoting [1905]) by Stephen Read - Thinking About Logic Ch.5 |
| 21549 | The theory of descriptions lacks conventions for the scope of quantifiers [Lackey on Russell] |
| Full Idea: Some logicians charge that the theory of descriptions as it stands is formally inadequate because it lacks explicit conventions for the scope of quantifiers, and that when these conventions are added the theory becomes unduly complex. | |
| From: comment on Bertrand Russell (On Denoting [1905]) by Douglas Lackey - Intros to Russell's 'Essays in Analysis' p.97 | |
| A reaction: [Especially in modal contexts, apparently] I suppose if the main point is to spell out the existence commitments of the description, then that has to include quantification, for full generality. |
| 12796 | Non-count descriptions don't threaten Russell's theory, which is only about singulars [Laycock on Russell] |
| Full Idea: It is sometimes claimed that the behaviour of definite non-count descriptions shows Russell's Theory of Descriptions itself to be false. ....but it isn't a general theory of descriptions, but precisely a theory of singular descriptions. | |
| From: comment on Bertrand Russell (On Denoting [1905]) by Henry Laycock - Words without Objects 3.1 |
| 7532 | Denoting is crucial in Russell's account of mathematics, for identifying classes [Russell, by Monk] |
| Full Idea: Denoting phrases are central to mathematics, especially in Russell's 'logicist' theory, in which they are crucial to identifying classes ('the class of all mortal beings', 'the class of natural numbers'). | |
| From: report of Bertrand Russell (On Denoting [1905]) by Ray Monk - Bertrand Russell: Spirit of Solitude Ch.6 | |
| A reaction: This explains the motivation for Russell's theory of definite descriptions, since he thinks reference is achieved by description. Russell nearly achieved an extremely complete philosophical system. |
| 11988 | Russell's analysis means molecular sentences are ambiguous over the scope of the description [Kaplan on Russell] |
| Full Idea: Russell's analysis of sentences containing definite descriptions has as an immediate consequence the doctrine that molecular sentences containing definite descriptions are syntactically ambiguous as regards the scope of the definite description. | |
| From: comment on Bertrand Russell (On Denoting [1905]) by David Kaplan - How to Russell a Frege-Church I | |
| A reaction: Presumably this is a virtue of Russell's account, and an advert for analytic philosophy, because it reveals an ambiguity which was there all the time. |
| 6061 | Existence is entirely expressed by the existential quantifier [Russell, by McGinn] |
| Full Idea: Nowadays Russell's position is routinely put by saying that existence is what is expressed by the existential quantifier and only by that. | |
| From: report of Bertrand Russell (On Denoting [1905]) by Colin McGinn - Logical Properties Ch.2 | |
| A reaction: We must keep separate how you express existence, and what it is. Quantifiers seem only to be a style of expressing existence; they don't offer any insight into what existence actually is, or what we mean by 'exist'. McGinn dislikes quantifiers. |
| 10082 | There are infinite sets that are not enumerable [Cantor, by Smith,P] |
| Full Idea: Cantor's Theorem (1874) says there are infinite sets that are not enumerable. This is proved by his 1891 'diagonal argument'. | |
| From: report of George Cantor (works [1880]) by Peter Smith - Intro to Gödel's Theorems 2.3 | |
| A reaction: [Smith summarises the diagonal argument] |
| 13483 | Cantor's Paradox: the power set of the universe must be bigger than the universe, yet a subset of it [Cantor, by Hart,WD] |
| Full Idea: The problem of Cantor's Paradox is that the power set of the universe has to be both bigger than the universe (by Cantor's theorem) and not bigger (since it is a subset of the universe). | |
| From: report of George Cantor (works [1880]) by William D. Hart - The Evolution of Logic 3 | |
| A reaction: Russell eliminates the 'universe' in his theory of types. I don't see why you can't just say that the members of the set are hypothetical rather than real, and that hypothetically the universe might contain more things than it does. |
| 8710 | The powerset of all the cardinal numbers is required to be greater than itself [Cantor, by Friend] |
| Full Idea: Cantor's Paradox says that the powerset of a set has a cardinal number strictly greater than the original set, but that means that the powerset of the set of all the cardinal numbers is greater than itself. | |
| From: report of George Cantor (works [1880]) by Michèle Friend - Introducing the Philosophy of Mathematics | |
| A reaction: Friend cites this with the Burali-Forti paradox and the Russell paradox as the best examples of the problems of set theory in the early twentieth century. Did this mean that sets misdescribe reality, or that we had constructed them wrongly? |
| 15910 | Cantor named the third realm between the finite and the Absolute the 'transfinite' [Cantor, by Lavine] |
| Full Idea: Cantor believed he had discovered that between the finite and the 'Absolute', which is 'incomprehensible to the human understanding', there is a third category, which he called 'the transfinite'. | |
| From: report of George Cantor (works [1880]) by Shaughan Lavine - Understanding the Infinite III.4 |
| 15905 | Cantor proved the points on a plane are in one-to-one correspondence to the points on a line [Cantor, by Lavine] |
| Full Idea: In 1878 Cantor published the unexpected result that one can put the points on a plane, or indeed any n-dimensional space, into one-to-one correspondence with the points on a line. | |
| From: report of George Cantor (works [1880]) by Shaughan Lavine - Understanding the Infinite III.1 |
| 9983 | Cantor took the ordinal numbers to be primary [Cantor, by Tait] |
| Full Idea: Cantor took the ordinal numbers to be primary: in his generalization of the cardinals and ordinals into the transfinite, it is the ordinals that he calls 'numbers'. | |
| From: report of George Cantor (works [1880]) by William W. Tait - Frege versus Cantor and Dedekind VI | |
| A reaction: [Tait says Dedekind also favours the ordinals] It is unclear how the matter might be settled. Humans cannot give the cardinality of large groups without counting up through the ordinals. A cardinal gets its meaning from its place in the ordinals? |
| 17798 | Cantor presented the totality of natural numbers as finite, not infinite [Cantor, by Mayberry] |
| Full Idea: Cantor taught us to regard the totality of natural numbers, which was formerly thought to be infinite, as really finite after all. | |
| From: report of George Cantor (works [1880]) by John Mayberry - What Required for Foundation for Maths? p.414-2 | |
| A reaction: I presume this is because they are (by definition) countable. |
| 9971 | Cantor introduced the distinction between cardinals and ordinals [Cantor, by Tait] |
| Full Idea: Cantor introduced the distinction between cardinal and ordinal numbers. | |
| From: report of George Cantor (works [1880]) by William W. Tait - Frege versus Cantor and Dedekind Intro | |
| A reaction: This seems remarkably late for what looks like a very significant clarification. The two concepts coincide in finite cases, but come apart in infinite cases (Tait p.58). |
| 9892 | Cantor showed that ordinals are more basic than cardinals [Cantor, by Dummett] |
| Full Idea: Cantor's work revealed that the notion of an ordinal number is more fundamental than that of a cardinal number. | |
| From: report of George Cantor (works [1880]) by Michael Dummett - Frege philosophy of mathematics Ch.23 | |
| A reaction: Dummett makes it sound like a proof, which I find hard to believe. Is the notion that I have 'more' sheep than you logically prior to how many sheep we have? If I have one more, that implies the next number, whatever that number may be. Hm. |
| 14136 | A cardinal is an abstraction, from the nature of a set's elements, and from their order [Cantor] |
| Full Idea: The cardinal number of M is the general idea which, by means of our active faculty of thought, is deduced from the collection M, by abstracting from the nature of its diverse elements and from the order in which they are given. | |
| From: George Cantor (works [1880]), quoted by Bertrand Russell - The Principles of Mathematics §284 | |
| A reaction: [Russell cites 'Math. Annalen, XLVI, §1'] See Fine 1998 on this. |
| 15906 | Cantor tried to prove points on a line matched naturals or reals - but nothing in between [Cantor, by Lavine] |
| Full Idea: Cantor said he could show that every infinite set of points on the line could be placed into one-to-one correspondence with either the natural numbers or the real numbers - with no intermediate possibilies (the Continuum hypothesis). His proof failed. | |
| From: report of George Cantor (works [1880]) by Shaughan Lavine - Understanding the Infinite III.1 |
| 11015 | Cantor's diagonal argument proved you can't list all decimal numbers between 0 and 1 [Cantor, by Read] |
| Full Idea: Cantor's diagonal argument showed that all the infinite decimals between 0 and 1 cannot be written down even in a single never-ending list. | |
| From: report of George Cantor (works [1880]) by Stephen Read - Thinking About Logic Ch.6 |
| 15903 | A real is associated with an infinite set of infinite Cauchy sequences of rationals [Cantor, by Lavine] |
| Full Idea: Cantor's theory of Cauchy sequences defines a real number to be associated with an infinite set of infinite sequences of rational numbers. | |
| From: report of George Cantor (works [1880]) by Shaughan Lavine - Understanding the Infinite II.6 | |
| A reaction: This sounds remarkably like the endless decimals we use when we try to write down an actual real number. |
| 18251 | Irrational numbers are the limits of Cauchy sequences of rational numbers [Cantor, by Lavine] |
| Full Idea: Cantor introduced irrationals to play the role of limits of Cauchy sequences of rational numbers. | |
| From: report of George Cantor (works [1880]) by Shaughan Lavine - Understanding the Infinite 4.2 |
| 15902 | Irrationals and the Dedekind Cut implied infinite classes, but they seemed to have logical difficulties [Cantor, by Lavine] |
| Full Idea: From the very nature of an irrational number, it seems necessary to understand the mathematical infinite thoroughly before an adequate theory of irrationals is possible. Infinite classes are obvious in the Dedekind Cut, but have logical difficulties | |
| From: report of George Cantor (works [1880]) by Shaughan Lavine - Understanding the Infinite II Intro | |
| A reaction: Almost the whole theory of analysis (calculus) rested on the irrationals, so a theory of the infinite was suddenly (in the 1870s) vital for mathematics. Cantor wasn't just being eccentric or mystical. |
| 15908 | It was Cantor's diagonal argument which revealed infinities greater than that of the real numbers [Cantor, by Lavine] |
| Full Idea: Cantor's 1891 diagonal argument revealed there are infinitely many infinite powers. Indeed, it showed more: it shows that given any set there is another of greater power. Hence there is an infinite power strictly greater than that of the set of the reals. | |
| From: report of George Cantor (works [1880]) by Shaughan Lavine - Understanding the Infinite III.2 |
| 13464 | Cantor proposes that there won't be a potential infinity if there is no actual infinity [Cantor, by Hart,WD] |
| Full Idea: What we might call 'Cantor's Thesis' is that there won't be a potential infinity of any sort unless there is an actual infinity of some sort. | |
| From: report of George Cantor (works [1880]) by William D. Hart - The Evolution of Logic 1 | |
| A reaction: This idea is nicely calculated to stop Aristotle in his tracks. |
| 10112 | The naturals won't map onto the reals, so there are different sizes of infinity [Cantor, by George/Velleman] |
| Full Idea: Cantor showed that the complete totality of natural numbers cannot be mapped 1-1 onto the complete totality of the real numbers - so there are different sizes of infinity. | |
| From: report of George Cantor (works [1880]) by A.George / D.J.Velleman - Philosophies of Mathematics Ch.4 |
| 8733 | The Continuum Hypothesis says there are no sets between the natural numbers and reals [Cantor, by Shapiro] |
| Full Idea: Cantor's 'continuum hypothesis' is the assertion that there are no infinite cardinalities strictly between the size of the natural numbers and the size of the real numbers. | |
| From: report of George Cantor (works [1880]) by Stewart Shapiro - Thinking About Mathematics 2.4 | |
| A reaction: The tricky question is whether this hypothesis can be proved. |
| 17889 | CH: An infinite set of reals corresponds 1-1 either to the naturals or to the reals [Cantor, by Koellner] |
| Full Idea: Cantor's Continuum Hypothesis (CH) says that for every infinite set X of reals there is either a one-to-one correspondence between X and the natural numbers, or between X and the real numbers. | |
| From: report of George Cantor (works [1880]) by Peter Koellner - On the Question of Absolute Undecidability 1.2 | |
| A reaction: Every single writer I read defines this differently, which drives me crazy, but is also helpfully illuminating. There is a moral there somewhere. |
| 13447 | Cantor: there is no size between naturals and reals, or between a set and its power set [Cantor, by Hart,WD] |
| Full Idea: Cantor conjectured that there is no size between those of the naturals and the reals - called the 'continuum hypothesis'. The generalized version says that for no infinite set A is there a set larger than A but smaller than P(A). | |
| From: report of George Cantor (works [1880]) by William D. Hart - The Evolution of Logic 1 | |
| A reaction: Thus there are gaps between infinite numbers, and the power set is the next size up from any infinity. Much discussion as ensued about whether these two can be proved. |
| 10883 | Cantor's Continuum Hypothesis says there is a gap between the natural and the real numbers [Cantor, by Horsten] |
| Full Idea: Cantor's Continuum Hypothesis states that there are no sets which are too large for there to be a one-to-one correspondence between the set and the natural numbers, but too small for there to exist a one-to-one correspondence with the real numbers. | |
| From: report of George Cantor (works [1880]) by Leon Horsten - Philosophy of Mathematics §5.1 |
| 13528 | Continuum Hypothesis: there are no sets between N and P(N) [Cantor, by Wolf,RS] |
| Full Idea: Cantor's conjecture (the Continuum Hypothesis) is that there are no sets between N and P(N). The 'generalized' version replaces N with an arbitrary infinite set. | |
| From: report of George Cantor (works [1880]) by Robert S. Wolf - A Tour through Mathematical Logic 2.2 | |
| A reaction: The initial impression is that there is a single gap in the numbers, like a hole in ozone layer, but the generalised version implies an infinity of gaps. How can there be gaps in the numbers? Weird. |
| 9555 | Continuum Hypothesis: no cardinal greater than aleph-null but less than cardinality of the continuum [Cantor, by Chihara] |
| Full Idea: Cantor's Continuum Hypothesis was that there is no cardinal number greater than aleph-null but less than the cardinality of the continuum. | |
| From: report of George Cantor (works [1880]) by Charles Chihara - A Structural Account of Mathematics 05.1 | |
| A reaction: I have no view on this (have you?), but the proposal that there are gaps in the number sequences has to excite all philosophers. |
| 18174 | Cantor extended ordinals into the transfinite, and they can thus measure infinite cardinalities [Cantor, by Maddy] |
| Full Idea: Cantor's second innovation was to extend the sequence of ordinal numbers into the transfinite, forming a handy scale for measuring infinite cardinalities. | |
| From: report of George Cantor (works [1880]) by Penelope Maddy - Naturalism in Mathematics I.1 | |
| A reaction: Struggling with this. The ordinals seem to locate the cardinals, but in what sense do they 'measure' them? |
| 15893 | Cantor's theory concerns collections which can be counted, using the ordinals [Cantor, by Lavine] |
| Full Idea: Cantor's set theory was not of collections in some familiar sense, but of collections that can be counted using the indexes - the finite and transfinite ordinal numbers. ..He treated infinite collections as if they were finite. | |
| From: report of George Cantor (works [1880]) by Shaughan Lavine - Understanding the Infinite I |
| 18173 | Cardinality strictly concerns one-one correspondence, to test infinite sameness of size [Cantor, by Maddy] |
| Full Idea: Cantor's first innovation was to treat cardinality as strictly a matter of one-to-one correspondence, so that the question of whether two infinite sets are or aren't of the same size suddenly makes sense. | |
| From: report of George Cantor (works [1880]) by Penelope Maddy - Naturalism in Mathematics I.1 | |
| A reaction: It makes sense, except that all sets which are infinite but countable can be put into one-to-one correspondence with one another. What's that all about, then? |
| 10232 | Property extensions outstrip objects, so shortage of objects caused the Caesar problem [Cantor, by Shapiro] |
| Full Idea: Cantor's theorem entails that there are more property extensions than objects. So there are not enough objects in any domain to serve as extensions for that domain. So Frege's view that numbers are objects led to the Caesar problem. | |
| From: report of George Cantor (works [1880]) by Stewart Shapiro - Philosophy of Mathematics 4.6 | |
| A reaction: So the possibility that Caesar might have to be a number arises because otherwise we are threatening to run out of numbers? Is that really the problem? |
| 18176 | Pure mathematics is pure set theory [Cantor] |
| Full Idea: Pure mathematics ...according to my conception is nothing other than pure set theory. | |
| From: George Cantor (works [1880], I.1), quoted by Penelope Maddy - Naturalism in Mathematics I.1 | |
| A reaction: [an unpublished paper of 1884] So right at the beginning of set theory this claim was being made, before it was axiomatised, and so on. Zermelo endorsed the view, and it flourished unchallenged until Benacerraf (1965). |
| 8631 | Cantor says that maths originates only by abstraction from objects [Cantor, by Frege] |
| Full Idea: Cantor calls mathematics an empirical science in so far as it begins with consideration of things in the external world; on his view, number originates only by abstraction from objects. | |
| From: report of George Cantor (works [1880]) by Gottlob Frege - Grundlagen der Arithmetik (Foundations) §21 | |
| A reaction: Frege utterly opposed this view, and he seems to have won the day, but I am rather thrilled to find the great Cantor endorsing my own intuitions on the subject. The difficulty is to explain 'abstraction'. |
| 18775 | Russell showed that descriptions may not have ontological commitment [Russell, by Linsky,B] |
| Full Idea: Russell's theory of definite descriptions allows us to avoid being ontologically committed to objects simply by virtue of using descriptions which seemingly denote them. | |
| From: report of Bertrand Russell (On Denoting [1905]) by Bernard Linsky - Quantification and Descriptions 1.1.2 | |
| A reaction: This I take to be why Russell's theory is a famous landmark. I personally take ontological commitment to be independent of what we specifically say. Others, like Quine, prefer to trim what we say until the commitments seem sound. |
| 7533 | The Theory of Description dropped classes and numbers, leaving propositions, individuals and universals [Russell, by Monk] |
| Full Idea: The real Platonic entities left standing after the Theory of Descriptions were propositions (not classes or numbers), and their constituents did not include denoting concepts or classes, but only individuals (Socrates) and universals (mortality). | |
| From: report of Bertrand Russell (On Denoting [1905]) by Ray Monk - Bertrand Russell: Spirit of Solitude Ch.6 | |
| A reaction: Propositions look like being the problem here. If we identify them with facts, it is not clear how many facts there are in the universe, independent of human thought. Indeed, how many universals are there? Nay, how many individuals? See Idea 7534. |
| 6063 | Russell can't attribute existence to properties [McGinn on Russell] |
| Full Idea: Russell's view makes it impossible to attribute existence to properties, and this would have to be declared ill-formed and meaningless. | |
| From: comment on Bertrand Russell (On Denoting [1905]) by Colin McGinn - Logical Properties Ch.2 | |
| A reaction: This strikes me as a powerful criticism, used to support McGinn's view that existence cannot be analysed, using quantifiers or anything else. |
| 18777 | If the King of France is not bald, and not not-bald, this violates excluded middle [Linsky,B on Russell] |
| Full Idea: Russell says one won't find the present King of France on the list of bald things, nor on the list of things that are not bald. It would seem that this gives rise to a violation of the law of excluded middle. | |
| From: comment on Bertrand Russell (On Denoting [1905]) by Bernard Linsky - Quantification and Descriptions 2 | |
| A reaction: It's a bit hard to accuse the poor old King of violating a law when he doesn't exist. |
| 4885 | Identity is a very weak relation, which doesn't require interdefinability, or shared properties [Perry] |
| Full Idea: The truth of "a=b" doesn't require much of 'a' and 'b' other than that there is a single thing to which they both refer. They needn't be interdefinable, or have supervenient properties. In this sense, identity is a very weak relation. | |
| From: John Perry (Knowledge, Possibility and Consciousness [2001], §1.2) | |
| A reaction: Interesting. This is seeing the epistemological aspects of identity. Ontologically, identity must invoke Leibniz's Law, and is the ultimately powerful 'relation'. A given student, and the cause of a crop circle, may APPEAR to be quite different. |
| 4899 | Possible worlds thinking has clarified the logic of modality, but is problematic in epistemology [Perry] |
| Full Idea: Using possible worlds to model truth-conditions of statements has led to considerable clarity about the logic of modality. Attempts to use the system for epistemic purposes, however, have been plagued by problems. | |
| From: John Perry (Knowledge, Possibility and Consciousness [2001], §8.1) | |
| A reaction: Presumably what lurks behind this is a distinction between what is logically or naturally possible, and what appears to be possible from the perspective of a conscious mind. Is there a possible world in which I can fly? |
| 4898 | Possible worlds are indices for a language, or concrete realities, or abstract possibilities [Perry] |
| Full Idea: Possible worlds can be thought of as indices for models of the language in question, or as concrete realities (David Lewis), or as abstract ways the world might be (Robert Stalnaker), or in various other ways. | |
| From: John Perry (Knowledge, Possibility and Consciousness [2001], §8.1) | |
| A reaction: I strongly favour the Stalnaker route here. Reducing great metaphysics to mere language I find abhorrent, and I suspect that Lewis was trapped by his commitment to strong empiricism. We must embrace abstractions into our ontology. |
| 4887 | We try to cause other things to occur by causing mental events to occur [Perry] |
| Full Idea: We try to cause other things to occur by causing mental events to occur. | |
| From: John Perry (Knowledge, Possibility and Consciousness [2001], §2.4) | |
| A reaction: A small and obvious, but important, point. Mental causation isn't just thoughts leading to physical happenings. Here Perry means that events can be designed to cause thoughts, such as a threatening letter. Not much room for epiphenomenalism here. |
| 4884 | Brain states must be in my head, and yet the pain seems to be in my hand [Perry] |
| Full Idea: The brain state will involve certain parts of the brain, whereas my feeling of pain seems to be located in my hand insofar as it has a bodily location. | |
| From: John Perry (Knowledge, Possibility and Consciousness [2001], §1.2) | |
| A reaction: This seems important to me. The brain is a ventriloquist. Perry implies that pain is quasi-disembodied, but it isn't, it is just experienced as IN the hand. Perhaps it is in the hand? Cutting the nerves loses contact with the pain. |
| 4888 | It seems plausible that many animals have experiences without knowing about them [Perry] |
| Full Idea: It seems quite plausible to me that many animals have experiences without knowing about them. | |
| From: John Perry (Knowledge, Possibility and Consciousness [2001], §3.1) | |
| A reaction: I agree, which makes us acknowledge levels of consciousness, which probably applies to human experience as well. The simplest idea is to distinguish between experiences which involve concepts, and those which don't. Animals sometimes appear surprised. |
| 4891 | If epiphenomenalism just says mental events are effects but not causes, it is consistent with physicalism [Perry] |
| Full Idea: Epiphenomenalism is usually considered to be a form of dualism, but if we define it as the doctrine that conscious events are effects but not causes, it appears to be consistent with physicalism. | |
| From: John Perry (Knowledge, Possibility and Consciousness [2001], §4.2) | |
| A reaction: Interesting. The theory was invented to put mind outside physics, and make the closure of physics possible. However, being capable of causing things seems to be a necessary condition for physical objects. An effect in one domain is a cause in another. |
| 4900 | Prior to Kripke, the mind-brain identity theory usually claimed that the identity was contingent [Perry] |
| Full Idea: Advocates of the mind-body identity theory typically claimed that identity between particular mental states and brain states was contingent, until Kripke argued persuasively that identity is always necessary. | |
| From: John Perry (Knowledge, Possibility and Consciousness [2001], §8.1) | |
| A reaction: Kripke wanted to argue against the identity theory, but what he seems to have done is reformulate it into a much more powerful version (involving necessary identity). |
| 4892 | If physicalists stick with identity (not supervenience), Martian pain will not be like ours [Perry] |
| Full Idea: The physicalist should not retreat to causal supervenience but should stick with identity. This means we will have to accept that a Martian and I (when in pain) are not in the same phenomenal state. | |
| From: John Perry (Knowledge, Possibility and Consciousness [2001], §4.3) | |
| A reaction: We naturally presume that frogs feel pain as we do, but many different phenomenal states could lead to the same behavioural end. Only an unpleasant feeling is required. A foul smell would do. Frogs could function with inverted qualia, too. |
| 4889 | Although we may classify ideas by content, we individuate them differently, as their content can change [Perry] |
| Full Idea: Although we classify ideas by content for many purposes, we do not individuate them by content. The content of an idea can change. | |
| From: John Perry (Knowledge, Possibility and Consciousness [2001], §3.2) | |
| A reaction: As the compiler of this database, I find this very appealing. The mind works exactly like a database. I have a 'file' (Perry's word) marked "London", the content of which undergoes continual change. I am a database management system. |
| 4896 | The intension of an expression is a function from possible worlds to an appropriate extension [Perry] |
| Full Idea: In possible-worlds semantics, expressions have intensions, which are functions from possible worlds to appropriate extensions (names to individuals, n-place predicates to n-tuples, and sentences to truth values, built from parts). | |
| From: John Perry (Knowledge, Possibility and Consciousness [2001], §8.1) | |
| A reaction: Interesting. Perry distinguishes 'referential' (or 'subject matter') content, which is prior to the link to extensions - a link which creates 'reflexive' content. He is keen that they should not become confused. True knowledge is 'situated'. |
| 8715 | Infinities expand the bounds of the conceivable; we explore concepts to explore conceivability [Cantor, by Friend] |
| Full Idea: Cantor (in his exploration of infinities) pushed the bounds of conceivability further than anyone before him. To discover what is conceivable, we have to enquire into the concept. | |
| From: report of George Cantor (works [1880]) by Michèle Friend - Introducing the Philosophy of Mathematics 6.5 | |
| A reaction: This remark comes during a discussion of Husserl's phenomenology. Intuitionists challenge Cantor's claim, and restrict what is conceivable to what is provable. Does possibility depend on conceivability? |
| 13454 | Cantor says (vaguely) that we abstract numbers from equal sized sets [Hart,WD on Cantor] |
| Full Idea: Cantor thought that we abstract a number as something common to all and only those sets any one of which has as many members as any other. ...However one wants to see the logic of the inference. The irony is that set theory lays out this logic. | |
| From: comment on George Cantor (works [1880]) by William D. Hart - The Evolution of Logic 1 | |
| A reaction: The logic Hart has in mind is the notion of an equivalence relation between sets. This idea sums up the older and more modern concepts of abstraction, the first as psychological, the second as logical (or trying very hard to be!). Cf Idea 9145. |
| 4567 | Russell argued with great plausibility that we rarely, if ever, refer with our words [Russell, by Cooper,DE] |
| Full Idea: Russell argued with great plausibility that we rarely, if ever, refer with our words. | |
| From: report of Bertrand Russell (On Denoting [1905]) by David E. Cooper - Philosophy and the Nature of Language §4 | |
| A reaction: I'm not sure if I understand this. Presumably phrases which appear to refer actually point at other parts of language rather than the world. |
| 5810 | Referring is not denoting, and Russell ignores the referential use of definite descriptions [Donnellan on Russell] |
| Full Idea: If I am right, referring is not the same as denoting and the referential use of definite descriptions is not recognised on Russell's view. | |
| From: comment on Bertrand Russell (On Denoting [1905]) by Keith Donnellan - Reference and Definite Descriptions §I | |
| A reaction: This introduces a new theory of reference, which goes beyond the mere contents of linguistic experessions. It says reference is an 'external' and 'causal' affair, and so a definite description is not sufficient to make a reference. |
| 16385 | A definite description 'denotes' an entity if it fits the description uniquely [Russell, by Recanati] |
| Full Idea: In Russell's definition of 'denoting', a definite description denotes an entity if that entity fits the description uniquely. | |
| From: report of Bertrand Russell (On Denoting [1905]) by François Recanati - Mental Files 17.2 | |
| A reaction: [Recanati cites Donnellan for this] Hence denoting is not the same thing as reference. A description can denote beautifully, but fail to refer. Donnellan says if denoting were reference, someone might refer without realising it. |
| 5774 | Denoting phrases are meaningless, but guarantee meaning for propositions [Russell] |
| Full Idea: Denoting phrases never have any meaning in themselves, but every proposition in whose verbal expression they occur has a meaning. | |
| From: Bertrand Russell (On Denoting [1905], p.43) | |
| A reaction: This is the important idea that the sentence is the basic unit of meaning, rather than the word. I'm not convinced that this dispute needs to be settled. Words are pretty pointless outside of propositions, and propositions are impossible without words. |
| 5775 | In 'Scott is the author of Waverley', denotation is identical, but meaning is different [Russell] |
| Full Idea: If we say 'Scott is the author of Waverley', we assert an identity of denotation with a difference of meaning. | |
| From: Bertrand Russell (On Denoting [1905], p.46) | |
| A reaction: This shows Russell picking up Frege's famous distinction, as shown in 'Hesperus is Phosphorus'. To distinguish the meaning from the reference was one of the greatest (and simplest) clarifications ever offered of how language works. |
| 16987 | By eliminating descriptions from primitive notation, Russell seems to reject 'sense' [Russell, by Kripke] |
| Full Idea: Russell, since he eliminates descriptions from his primitive notation, seems to hold in 'On Denoting' that the notion of 'sense' is illusory. | |
| From: report of Bertrand Russell (On Denoting [1905]) by Saul A. Kripke - Naming and Necessity notes and addenda note 04 | |
| A reaction: Presumably we can eliminate sense from formal languages, but natural languages are rich in connotations (or whatever we choose to call them). |
| 4570 | Russell assumes that expressions refer, but actually speakers refer by using expressions [Cooper,DE on Russell] |
| Full Idea: Russell assumes that it is expressions which refer if anything does, but strictly speaking it is WE who refer with the use of expressions. | |
| From: comment on Bertrand Russell (On Denoting [1905]) by David E. Cooper - Philosophy and the Nature of Language §4.1 | |
| A reaction: This sounds right. Russell is part of the overemphasis on language which plagued philosophy after Frege. Words are tools, like searchlights or pointing fingers. |
| 16349 | Russell rejected sense/reference, because it made direct acquaintance with things impossible [Russell, by Recanati] |
| Full Idea: Russell rejected Frege's sense/reference distinction, on the grounds that, if reference is mediated by sense, we lose the idea of direct acquaintance and succumb to Descriptivism. | |
| From: report of Bertrand Russell (On Denoting [1905]) by François Recanati - Mental Files 1.1 | |
| A reaction: [15,000th IDEA in the DB!! 23/3/2013, Weymouth] Recanati claims Russell made a mistake, because you can retain the sense/reference distinction, and still keep direct acquaintance (by means of 'non-descriptive senses'). |
| 7313 | 'Sense' is superfluous (rather than incoherent) [Russell, by Miller,A] |
| Full Idea: Russell does not claim that Frege's notion of sense is incoherent, but rather that it is superfluous. | |
| From: report of Bertrand Russell (On Denoting [1905]) by Alexander Miller - Philosophy of Language 2.9 | |
| A reaction: My initial reaction to this is that the notion of strict and literal meaning (see Idea 7309) is incredibly useful. Some of the best jokes depend on the gap between implications and strict meaning. How could metaphors be explained without it? |
| 7767 | The theory of definite descriptions aims at finding correct truth conditions [Russell, by Lycan] |
| Full Idea: Russell's theory of definite descriptions proceeds by sketching the truth conditions of sentences containing descriptions, and arguing on various grounds that they are the correct truth conditions. | |
| From: report of Bertrand Russell (On Denoting [1905]) by William Lycan - Philosophy of Language Ch.9 | |
| A reaction: It seems important to see both where Russell was going, and where Davidson has come from. The whole project of finding the logical form of sentences (which starts with Frege and Russell) implies that truth conditions is what matters. |
| 4897 | A proposition is a set of possible worlds for which its intension delivers truth [Perry] |
| Full Idea: The proposition expressed by a sentence can be thought of as a set of possible worlds, the worlds for which its intension delivers truth. | |
| From: John Perry (Knowledge, Possibility and Consciousness [2001], §8.1) | |
| A reaction: It has always struck me as important to hang on to the concept of a 'proposition' (over and above sentences). This idea gives a metaphysics for the concept, and the 'language of thought' offers appropriate brain structures. A neat picture. |
| 21726 | In graspable propositions the constituents are real entities of acquaintance [Russell] |
| Full Idea: In every proposition that we can apprehend, ...all the constituents are real entities with which we have immediate acquaintance. | |
| From: Bertrand Russell (On Denoting [1905], p.56), quoted by Bernard Linsky - Russell's Metaphysical Logic 7.2 | |
| A reaction: This is the clearest statement of the 'Russellian' concept of a proposition. It strikes me as entirely wrong. The examples are always nice concrete objects like Mont Blanc, but as an account of sophisticated general propositions it seem hopeless. |
| 4890 | A sharp analytic/synthetic line can rarely be drawn, but some concepts are central to thought [Perry] |
| Full Idea: Although there is seldom a sharp analytic/synthetic distinction to be drawn in the case of our concepts, there are clearly things that are more and less central. | |
| From: John Perry (Knowledge, Possibility and Consciousness [2001], §3.2) | |
| A reaction: Most Americans seem enslaved to Quine on this one, so it is nice to see the obvious being stated for once. Human thought is an organic offshoot of the natural world. To think it is all arbitrary and changeable is human arrogance. |
| 10863 | Cantor proved that three dimensions have the same number of points as one dimension [Cantor, by Clegg] |
| Full Idea: Cantor proved that one-dimensional space has exactly the same number of points as does two dimensions, or our familiar three-dimensional space. | |
| From: report of George Cantor (works [1880]) by Brian Clegg - Infinity: Quest to Think the Unthinkable Ch.14 |
| 13465 | Only God is absolutely infinite [Cantor, by Hart,WD] |
| Full Idea: Cantor said that only God is absolutely infinite. | |
| From: report of George Cantor (works [1880]) by William D. Hart - The Evolution of Logic 1 | |
| A reaction: We are used to the austere 'God of the philosophers', but this gives us an even more austere 'God of the mathematicians'. |
| 5773 | The ontological argument begins with an unproven claim that 'there exists an x..' [Russell] |
| Full Idea: 'There is one and only one entity x which is most perfect; that one has all perfections; existence is a perfection; therefore that one exists' fails as a proof because there is no proof of the first premiss. | |
| From: Bertrand Russell (On Denoting [1905], p.54) | |
| A reaction: This is the modern move of saying that existence (which is 'not a predicate', according to Kant) is actually a quantifier, which isolates the existence claim being made about a variable with a bunch of predicates. McGinn denies Russell's claim. |