94 ideas
| 18019 | People have dreams which involve category mistakes [Magidor] |
| Full Idea: It is an empirical fact that people often sincerely report having had dreams which involve category mistakes. | |
| From: Ofra Magidor (Category Mistakes [2013], 3.4) | |
| A reaction: She doesn't give any examples, but I was thinking that this might be the case before I read this idea. Dreams seem to allow you to live with gaps in reality that we don't tolerate when awake. |
| 17998 | Category mistakes are either syntactic, semantic, or pragmatic [Magidor] |
| Full Idea: A plausible case can be made for explaining the phenomenon of category mistakes in terms of each of syntax, semantics, and pragmatics. | |
| From: Ofra Magidor (Category Mistakes [2013], 1.1) | |
| A reaction: I want to explain them in terms of (structured) ontology, but she totally rejects that on p.156. Her preferred account is that they are presupposition failures, which is pragmatics. She splits the semantic view into truth-valued and non-truth-valued. |
| 18011 | Category mistakes seem to be universal across languages [Magidor] |
| Full Idea: The infelicity of category mistakes seems to be universal across languages. | |
| From: Ofra Magidor (Category Mistakes [2013], 2.3) | |
| A reaction: Magidor rightly offers this fact to refute the claim that category mistakes are purely syntax (since syntax obviously varies hugely across languages). I also take the fact to show that category mistakes concern the world, and not merely language. |
| 18012 | Category mistakes as syntactic needs a huge number of fine-grained rules [Magidor] |
| Full Idea: A syntactic theory of category mistakes would require not only general syntactic features such as must-be-human, but also highly particular ones such as must-be-a-grape. | |
| From: Ofra Magidor (Category Mistakes [2013], 2.3) | |
| A reaction: Her grape example comes from Hebrew, but an English example might be the verb 'to hull', which is largely exclusive to strawberries. The 'must-be' form is one of Chomsky's 'selectional features'. |
| 18013 | Embedded (in 'he said that…') category mistakes show syntax isn't the problem [Magidor] |
| Full Idea: The embedding data (such as 'John said that the number two is green', compared to '*John said that me likes apples') strongly suggests that category mistakes are not syntactically ill-formed. | |
| From: Ofra Magidor (Category Mistakes [2013], 2.4) | |
| A reaction: Sounds conclusive. The report of John's category error, unlike the report of his remark about apples, seems perfectly syntactically acceptable. |
| 18016 | Two good sentences should combine to make a good sentence, but that might be absurd [Magidor] |
| Full Idea: The principle that if 'p' and 'q' are meaningful sentences then 'p and q' is a meaningful sentence seems highly plausible. But now consider the following example: 'That is a number and that is green'. | |
| From: Ofra Magidor (Category Mistakes [2013], 3.2.2) | |
| A reaction: This challenges the defence of the meaningfulness of category mistakes on the basis of strong compositionality. |
| 18015 | The normal compositional view makes category mistakes meaningful [Magidor] |
| Full Idea: The principle that if a competent speaker understands some terms then they understand a sentence made up of them entails that category mistakes are meaningful (as in understanding 'the number two' and 'is green'). | |
| From: Ofra Magidor (Category Mistakes [2013], 3.2.1) | |
| A reaction: [compressed version] It is normal to impose restrictions on plausible compositionality, and thus back away from this claim, but I rather sympathise with it. She adds to a second version of the principle the proviso 'IF the sentence is meaningful'. |
| 18017 | If a category mistake is synonymous across two languages, that implies it is meaningful [Magidor] |
| Full Idea: Two sentences are synonymous if they have the same meaning, suggesting that they must both be meaningful. On the face of it the English 'two is green' and French 'deux est vert' are synonymous, suggesting meaningful category mistakes. | |
| From: Ofra Magidor (Category Mistakes [2013], 3.3) | |
| A reaction: I'm fairly convinced already that most category mistakes are meaningful, and this seems to confirm the view. Some mistakes could be so extreme that no auditor could compute their meaning, especially if you concatenated lots of them. |
| 18021 | Category mistakes are meaningful, because metaphors are meaningful category mistakes [Magidor] |
| Full Idea: Metaphors must have literal meanings. …Since many metaphors involving category mistakes manage to achieve their metaphorical purpose, they must also have literal meanings, so category mistakes must be (literally) meaningful. | |
| From: Ofra Magidor (Category Mistakes [2013], 3.5) | |
| A reaction: Hm. 'This guy is so weird that to meet him is to encounter a circular square'. |
| 18031 | If a category mistake has unimaginable truth-conditions, then it seems to be meaningless [Magidor] |
| Full Idea: One motivation for taking category mistakes to be meaningless is that one cannot even imagine what it would take for 'Two is green' to be true. …Underlying this complaint is sometimes the thought that the meaning of a sentence is its truth-conditions. | |
| From: Ofra Magidor (Category Mistakes [2013], 3.6) | |
| A reaction: I defend the view that most sentences are meaningful if they compose from meaningful parts, but you have to acknowledge this view. It seems to come in degrees. Sentences can have fragmentary meaning, or be almost meaningful, or offer a glimpse of meaning? |
| 18030 | A good explanation of why category mistakes sound wrong is that they are meaningless [Magidor] |
| Full Idea: The meaninglessness view does seem to offer a simple and compelling explanation for the fact that category mistakes are highly infelicitous. | |
| From: Ofra Magidor (Category Mistakes [2013], 3.6) | |
| A reaction: However, I take there to be quite a large gulf between why meaningless sentences like 'squares turn happiness into incommensurability', which I would call 'category blunders', and subtle category mistakes, which are meaningful. |
| 18032 | Category mistakes are neither verifiable nor analytic, so verificationism says they are meaningless [Magidor] |
| Full Idea: No sense experience shows that 'two is green' is true or false. But neither is 'two is green' analytically true or false. So it fails to have legitimate verification conditions and hence, by the lights of traditional verificationism, it is meaningless. | |
| From: Ofra Magidor (Category Mistakes [2013], 3.6.2) | |
| A reaction: If a category mistake is an error in classification, then it would seem to be analytically false. If it wrongly attributes a property to something, that makes it verifiably false. The problem is to verify anything at all about 'two'. |
| 18034 | Category mistakes play no role in mental life, so conceptual role semantics makes them meaningless [Magidor] |
| Full Idea: One might argue that conceptual role semantics entails that category mistakes are meaningless. Sentences such as 'two is green' play no role in the cognitive life of any agent. | |
| From: Ofra Magidor (Category Mistakes [2013], 3.6.2) | |
| A reaction: [She quotes Block's definition of conceptual role semantics] I would have thought that if a category mistake is believed by an agent, it could play a huge role in their cognitive life. |
| 18037 | Maybe when you say 'two is green', the predicate somehow fails to apply? [Magidor] |
| Full Idea: One might argue that although 'two' refers to the number two, and 'is green' expresses the property of being green, in 'two is green' the property somehow fails to apply to the number two. | |
| From: Ofra Magidor (Category Mistakes [2013], 4.2) | |
| A reaction: It is an interesting thought that you say something which applies a predicate to an object, but the predicate then 'fails to apply' for reasons of its own, over which you have no control. The only possible cause of the failure is the nature of reality. |
| 18039 | If category mistakes aren't syntax failure or meaningless, maybe they just lack a truth-value? [Magidor] |
| Full Idea: Having rejected the syntactic approach and the meaninglessness view, one might feel that the last resort for explaining the defectiveness of category mistakes is to claim that they are truth-valueless (even if meaningful). | |
| From: Ofra Magidor (Category Mistakes [2013], 4.3.1) | |
| A reaction: She rejects this one as well, and votes for a pragmatic explanation, in terms of presupposition failure. The view I incline towards is just that they are false, despite being well-formed, meaningful and truth-valued. |
| 18041 | Category mistakes suffer from pragmatic presupposition failure (which is not mere triviality) [Magidor] |
| Full Idea: I argue that category mistakes are infelicitous because they suffer from (pragmatic) presupposition failure, ...but I reject the 'naive pragmatic approach' according to which category mistakes are infelicitous because they are trivially true or false. | |
| From: Ofra Magidor (Category Mistakes [2013], 5.1) | |
| A reaction: She supports her case quite well, but I vote for them being false. The falsity may involve presuppositions. 'Two is green' is a category mistake, and false, because 'two' lacks the preconditions for anything to be coloured (notably, emitting light). |
| 18058 | Maybe the presuppositions of category mistakes are the abilities of things? [Magidor] |
| Full Idea: The most promising way to characterise the presuppositions involved in category mistakes might be to rephrase them in modal terms ('x is able to be pregnant', 'x is able to be green'). | |
| From: Ofra Magidor (Category Mistakes [2013], 5.4.3) | |
| A reaction: This catches my attention because it suggests that category mistakes contradict dispositions, rather than contradicting classifications or types. 'Let's use a magnet to repel this iron'? The dispositions of 'two' and 'green' in 'two is green'? Hm |
| 18056 | Category mistakes because of presuppositions still have a truth value (usually 'false') [Magidor] |
| Full Idea: I am assuming that even in those contexts in which the presupposition of 'the number two is green' fails and the utterance is infelicitious, it nevertheless receives a bivalent truth-value (presumably 'false'). | |
| From: Ofra Magidor (Category Mistakes [2013], 5.4.1) | |
| A reaction: It seems to me obvious that, in normal contexts, 'the number two is green' is false, rather than meaningless. Is 'the number eight is an odd number' meaningless? |
| 18055 | In 'two is green', 'green' has a presupposition of being coloured [Magidor] |
| Full Idea: My proposal is that the truth-conditional content of 'green' (in 'two is green') is the property of being green, and its presuppositional content is the property of being coloured. | |
| From: Ofra Magidor (Category Mistakes [2013], 5.4.1) | |
| A reaction: This requires a two-dimensional semantics of truth-conditional and presuppositional content. I fear it may have a problem she spotted elsewhere, of overgenerating presuppositions. Eyes are presupposed by 'green'. Ambient light is required. |
| 18057 | 'Numbers are coloured and the number two is green' seems to be acceptable [Magidor] |
| Full Idea: 'The number two is green' is normally infelicitous, but, interestingly, 'numbers are coloured and the number two is green' is not infelicitous. | |
| From: Ofra Magidor (Category Mistakes [2013], 5.4.1) | |
| A reaction: A nice example, which gives good support for her pragmatic account of category mistakes in terms of presupposition failure. But how about 'figures can have contradictory shapes, and this square is circular'? Numbers are not coloured!!! |
| 18059 | The presuppositions in category mistakes reveal nothing about ontology [Magidor] |
| Full Idea: My pragmatic account of category mistakes does not support a key role for them in metaphysics. It is highly doubtful that the presuppositions associated with category mistakes reveal anything about the fundamental nature of ontological categories. | |
| From: Ofra Magidor (Category Mistakes [2013], 5.6) | |
| A reaction: Thus she dashes my hope, without even bothering to offer a reason. I think she should push her enquiry further, and ask why we presuppose things. Why do we take presuppositions for granted? Why are they obvious? |
| 18040 | Intensional logic maps logical space, showing which predicates are compatible or incompatible [Magidor] |
| Full Idea: Intensional logic aims to capture necessary relations between certain predicates, such as that 'green all over' and 'red all over' cannot be co-instantiated. Each predicate is allocated a set of points in logical space, and every object has one point. | |
| From: Ofra Magidor (Category Mistakes [2013], 4.4) | |
| A reaction: This produces an intriguing model of reality, as a vast and rich space of multiply overlapping modal predicates. Things can be blue, square, dangerous and large. They can't be small and large, or square and round. Objects are optional extras! |
| 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 |
| 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). |
| 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 |
| 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. |
| 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. |
| 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 |
| 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 |
| 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 |
| 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 |
| 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. |
| 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? |
| 17997 | Some suggest that the Julius Caesar problem involves category mistakes [Magidor] |
| Full Idea: Various authors have argued that identity statements arising in the context of the 'Julius Caesar' problem in philosophy of mathematics constitute category mistakes. | |
| From: Ofra Magidor (Category Mistakes [2013], 1.1 n1) | |
| A reaction: [She cites Benacerraf 1965 and Shapiro 1997:79] |
| 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'. |
| 16655 | Different genera are delimited by modes of predication, which rest on modes of being [Aquinas] |
| Full Idea: Being is delimited into different genera in accord with different modes of predicating, which depend on different modes of being. | |
| From: Thomas Aquinas (On Aristotle's 'Metaphysics' [1266], V.9.890), quoted by Robert Pasnau - Metaphysical Themes 1274-1671 12.3 | |
| A reaction: I like this. When people say that predication is the way we divide things up, and go all linguistic-relativist about things, they forget how closely language not only describes reality, but arises out of, or is even caused by, reality. 'Grue' is silly. |
| 18060 | We can explain the statue/clay problem by a category mistake with a false premise [Magidor] |
| Full Idea: Since 'the lump of clay is Romanesque' is a category mistake, a pragmatic account of that phenomenon is key to pursuing the strategy of saying that the problem rests on a false premise. | |
| From: Ofra Magidor (Category Mistakes [2013], 5.6) | |
| A reaction: [compressed] |
| 18020 | Propositional attitudes relate agents to either propositions, or meanings, or sentence/utterances [Magidor] |
| Full Idea: Three views of the semantics of propositional attitudes: they are relations between agents and propositions ('propositional' view); relations between individuals and meanings (Fregean); or relations of individuals and sentences/utterances ('sentential'). | |
| From: Ofra Magidor (Category Mistakes [2013], 3.4) | |
| A reaction: I am a propositionalist on this one. Meanings are too vague, and sentences are too linguistic. |
| 18035 | Two sentences with different meanings can, on occasion, have the same content [Magidor] |
| Full Idea: It is commonly assumed that meaning and content can come apart: the sentence 'I am writing' and 'Ofra is writing' may have different meanings, even if, as currently uttered, they express the same content. | |
| From: Ofra Magidor (Category Mistakes [2013], 4.1) | |
| A reaction: From that, I would judge 'content' to mean the same as 'proposition'. |
| 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? |
| 18018 | To grasp 'two' and 'green', must you know that two is not green? [Magidor] |
| Full Idea: Is it a necessary condition on possessing the concepts of 'two' and 'green' that one does not believe that two is green? I think this claim is false. | |
| From: Ofra Magidor (Category Mistakes [2013], 3.4) | |
| A reaction: To see that it is false one only has to consider much more sophisticated concepts, which are grasped without knowing their full implications. I might think two is green because I fully grasp 'two', but have not yet mastered 'green'. |
| 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. |
| 18008 | Generative semantics says structure is determined by semantics as well as syntactic rules [Magidor] |
| Full Idea: Generative semanticists claimed that the structure of a sentence is determined by both 'syntactic' and 'semantic' considerations which interact with each other in complex ways. | |
| From: Ofra Magidor (Category Mistakes [2013], 1.3) | |
| A reaction: [She mentions George Lakoff for this view] You need to study a range of examples, but this sounds a better view to me than the tidy picture of producing a syntactic structure and then adding a semantics. We make up sentences while speaking them. |
| 18010 | 'John is easy to please' and 'John is eager to please' have different deep structure [Magidor] |
| Full Idea: The sentences 'John is easy to please' and 'John is eager to please' can have very different deep structure (with the latter concerning John as a pleaser, while the former concerns John as the one being pleased). | |
| From: Ofra Magidor (Category Mistakes [2013], 2.1) | |
| A reaction: This demolishes the old idea of grammar as 'parts of speech' strung together according to superficial rules. The question is whether we now just have deeper syntax, or whether semantics is part of the process. |
| 18053 | The semantics of a sentence is its potential for changing a context [Magidor] |
| Full Idea: The basic semantics of sentences are not truth-conditions, but rather context change potential, which is a rule which determines what the effect of uttering the sentence would be on the context. | |
| From: Ofra Magidor (Category Mistakes [2013], 5.3.2) | |
| A reaction: [I. Heim's 'renowned' 1983 revision of Stalnaker] This means the semantics of a sentence can vary hugely, depending on context. It is known as 'dynamic semantics'. 'I think you should go ahead and do it'. |
| 18000 | Weaker compositionality says meaningful well-formed sentences get the meaning from the parts [Magidor] |
| Full Idea: A weaker principle of compositionality states that if a syntactically well-formed sentence is meaningful, then its meaning is a function of the meaning of its parts. | |
| From: Ofra Magidor (Category Mistakes [2013], 1.1) | |
| A reaction: I would certainly accept this as being correct. I take the meaning of a sentence to be something which you assemble in your head as you hear the parts of it unfold. ….However, irony might exhibit meaning that only comes from the whole sentence. Hm. |
| 17999 | Strong compositionality says meaningful expressions syntactically well-formed are meaningful [Magidor] |
| Full Idea: In the strong form of the principle of compositionality any meaningful expressions combined in a syntactically well-formed manner compose a meaningful expression. | |
| From: Ofra Magidor (Category Mistakes [2013], 1.1) | |
| A reaction: [She cites Montague as holding this view] I find this plausible, at least. If you look at whole sentences they can seem meaningless, but if you track the process of composition a collective meaning emerges, despite the oddities. |
| 18014 | Understanding unlimited numbers of sentences suggests that meaning is compositional [Magidor] |
| Full Idea: The fact that speakers of natural languages have the capacity to understand indefinitely many new sentences suggests that meaning must be compositional. | |
| From: Ofra Magidor (Category Mistakes [2013], 3.2.1) | |
| A reaction: To some extent, the compositionality of meaning is so obvious as to hardly require pointing out. It is the precise nature of the claim, and the extent to which whole sentences can add to the compositional meaning, that is of interest. |
| 18001 | Are there partial propositions, lacking truth value in some possible worlds? [Magidor] |
| Full Idea: Are there such things as 'partial propositions', which are truth-valueless relative to some possible worlds? | |
| From: Ofra Magidor (Category Mistakes [2013], 1.1) | |
| A reaction: Presumably this could be expressed without possible worlds. Are there propositions meaningful in New Guinea, and meaningless in England? Do some propositions require the contingent existence of certain objects to be meaningful? |
| 18036 | A sentence can be meaningful, and yet lack a truth value [Magidor] |
| Full Idea: 'That is red' in a context where the demonstrative fails to refer is truth-valueless, despite being meaningful, as is 'the queen of France in 2010 is bald'. ...The claim that some sentences are meaningful but truth-valueless is, then, widely accepted. | |
| From: Ofra Magidor (Category Mistakes [2013], 4.1) | |
| A reaction: The lack of truth value is usually because of reference failure. It is best to say the words are meaningful, but no proposition is expressed. |
| 18051 | In the pragmatic approach, presuppositions are assumed in a context, for successful assertion [Magidor] |
| Full Idea: According to the pragmatic approach, presuppositions are constraints on the context: if a sentence s generates a presupposition p, an assertion of s cannot proceed smoothly unless the context already entails p (p is taken for granted). | |
| From: Ofra Magidor (Category Mistakes [2013], 5.3.2) | |
| A reaction: She credits Stalnaker for this approach. There is a choice between the presuppositions being largely driven by internal features of the sentence, or by external features of context. You may not know the context of some statements. |
| 18043 | The infelicitiousness of trivial truth is explained by uninformativeness, or a static context-set [Magidor] |
| Full Idea: In Grice's theory if a sentence is trivially true, asserting it would violate the maxim of quantity. For Stalnaker, if p is trivially true, it involves no update to the context-set, and is thus pointless. | |
| From: Ofra Magidor (Category Mistakes [2013], 5.2) | |
| A reaction: 'Let us remind ourselves, before we proceed, of the following trivial truth: p'. |
| 18042 | The infelicitiousness of trivial falsity is explained by expectations, or the loss of a context-set [Magidor] |
| Full Idea: In Grice's theory if a sentence is trivially false, asserting it would violate the maxim of quality. For Stalnaker if p is trivially false, removing all worlds incompatible with p would result in an empty context-set, preventing any further communication. | |
| From: Ofra Magidor (Category Mistakes [2013], 5.2) | |
| A reaction: [compressed] I'm not sure whether we need to 'explain' the inappropriateness of uttering trivial falsities. I take the main rule of conversation to be 'don't be boring', but we all violate that. |
| 18050 | If both s and not-s entail a sentence p, then p is a presupposition [Magidor] |
| Full Idea: In the traditional account, a sentence s presupposes p if and only if both s and ¬s entail p. Standardly, this entails that if s presupposes p, then whenever p is false, s must be neither true nor false. | |
| From: Ofra Magidor (Category Mistakes [2013], 5.3.2) | |
| A reaction: 'I'm looking down on the garden' presupposes 'I'm upstairs'. Why would 'I'm not looking down on the garden' entail 'I'm upstairs'? I seem to have missed something. |
| 18047 | A presupposition is what makes an utterance sound wrong if it is not assumed? [Magidor] |
| Full Idea: The most obvious test for presupposition would be this: if s generates the presupposition p, then an utterance of s would be infelicitous, unless p is taken for granted by participants in the conversation. | |
| From: Ofra Magidor (Category Mistakes [2013], 5.3.1.1) | |
| A reaction: The principle of charity seems to be involved here - that we try to make people's utterances sound right, so we add in the presuppositions which would achieve that. The problem, she says, is that the infelicity may have other causes. |
| 18048 | A test for presupposition would be if it provoked 'hey wait a minute - I have no idea that....' [Magidor] |
| Full Idea: A proposed test for presupposition is the 'Hey, wait a minute' test. S presupposes that p, just in case it would be felictious to respond to an utterance of s with something like 'Hey, wait a minute - I had not idea that p!'. | |
| From: Ofra Magidor (Category Mistakes [2013], 5.3.1.2) | |
| A reaction: [K. Von Finkel 2004 made the suggestion] That is, you think 'hm ...this statement seems to presuppose p'. She says the suggestion vastly over-generates possible presuppositions - unlikely ones, as well as the obvious ones. |
| 18049 | The best tests for presupposition are projecting it to negation, conditional, conjunction, questions [Magidor] |
| Full Idea: The most robust tests for presupposition are the projection tests. If s presupposes p, then ¬s does too. If s1 presupposes p, then 'if s1 then s2' presupposes p. If s1 presupposes p, then 's1 and s2' presupposes p. If s presupposes p, then 's?' does too. | |
| From: Ofra Magidor (Category Mistakes [2013], 5.3.1.3) | |
| A reaction: [compressed] She also discusses quantifiers. In other words, the presupposition remains stable through various transformations of the underlying proposition. |
| 18054 | Why do certain words trigger presuppositions? [Magidor] |
| Full Idea: We can ask why a range of lexical items (e.g. 'stop' or 'know') trigger the presuppositions they do. | |
| From: Ofra Magidor (Category Mistakes [2013], 5.3.2) | |
| A reaction: I'm not sure whether we'll get an answer, but I would approach the question by thinking about mental files. |
| 18022 | Metaphors tend to involve category mistakes, by joining disjoint domains [Magidor] |
| Full Idea: The fact that most metaphors involve category mistakes is not a coincidence. …A big part of them is to do with connecting objects and properties that normally seem to belong to disjoint domains. | |
| From: Ofra Magidor (Category Mistakes [2013], 3.5) | |
| A reaction: Metaphysica poets took disjoint domains and 'yoked them together by violence', according to Dr Johnson. |
| 18023 | Theories of metaphor divide over whether they must have literal meanings [Magidor] |
| Full Idea: There are theories of metaphors that require them to have literal meanings in order to achieve their metaphorical purpose, and those that do not. | |
| From: Ofra Magidor (Category Mistakes [2013], 3.5) | |
| A reaction: I take almost any string of proper language to have literal meaning (for compositional reasons), even if the end result is somewhat ridiculous. 'Churchill was a lion' obviously has literal meaning. And so does 'Churchill was a transcendental number'. |
| 18024 | One theory says metaphors mean the same as the corresponding simile [Magidor] |
| Full Idea: On standard versions of the simile theory of metaphors, they mean the same as the corresponding simile. | |
| From: Ofra Magidor (Category Mistakes [2013], 3.5) | |
| A reaction: Magidor points out that this allows the metaphor to work while being meaningless, since all the work is done by the perfectly meaningful simile. But the metaphor must at least mean enough to indicate what the simile is. |
| 18027 | Metaphors as substitutes for the literal misses one predicate varying with context [Magidor] |
| Full Idea: A problem with the substitution view of metaphors is that the same predicate can have very different metaphorical contributions in different contexts. Consider 'Juliet is the sun' uttered by Romeo, and 'Stalin is the sun' from a devoted communist. | |
| From: Ofra Magidor (Category Mistakes [2013], 3.5) | |
| A reaction: The substitution view never looked good (especially if you like poetry), and now it looks a lot worse. |
| 18025 | The simile view of metaphors removes their magic, and won't explain why we use them [Magidor] |
| Full Idea: The simile theory of metaphors makes them too easy to figure out, when they cannot be paraphrased in literal terms, …and it does not explain why we use metaphors as well as similes. | |
| From: Ofra Magidor (Category Mistakes [2013], 3.5) | |
| A reaction: [She cites Davidson for these points] They might just be similes with the added frisson of leaving out 'like', so that they seem at first to be false, until you work out the simile and see their truth. |
| 18026 | Maybe a metaphor is just a substitute for what is intended literally, like 'icy' for 'unemotional' [Magidor] |
| Full Idea: According to the substitution view of metaphors, a word used metaphorically is merely a substitute for another word or phrase that expresses the same meaning literally. Thus 'John is an ice-cube' is a substitute for 'John is cruel and unemotional'. | |
| From: Ofra Magidor (Category Mistakes [2013], 3.5) | |
| A reaction: This seems to capture the denotation but miss the connotation. Whoever came up with this theory didn't read much poetry. |
| 18028 | Gricean theories of metaphor involve conversational implicatures based on literal meanings [Magidor] |
| Full Idea: Gricean theories of metaphor …assume that conversational implicatures are generated via literal contents, and hence that a sentence cannot generate an implicature without being literally meaningful. | |
| From: Ofra Magidor (Category Mistakes [2013], 3.5) | |
| A reaction: Magidor gives not details of such theories, but presumably the metaphor is all in the speaker's intention, which is parasitic on the wayward literal meaning, as in cases of irony. |
| 18029 | Non-cognitivist views of metaphor says there are no metaphorical meanings, just effects of the literal [Magidor] |
| Full Idea: According to non-cognitivists there is no such thing as metaphorical meaning. …The effects on the hearer are induced directly via the literal meaning of the metaphor. | |
| From: Ofra Magidor (Category Mistakes [2013], 3.5) | |
| A reaction: [This is said to be Davidson's view] I wonder how many people defended some explicit 'metaphorical meaning', as opposed to connotations that accumulate as you take in the metaphor? Any second meaning is just a further literal meaning. |
| 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'. |