68 ideas
| 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. |
| 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'. |
| 22427 | To explain object qualities, primary qualities must be more than mere sources of experience [McGinn] |
| Full Idea: In order that we have available an explanation of the qualities of objects we need to be able to conceive primary qualities as consisting in something other than powers to produce experiences. | |
| From: Colin McGinn (Subjective View: sec qualities and indexicals [1983], 6 n 52) | |
| A reaction: I suppose if the qualities are nothing more than the source of the experiences, that is Kant's noumenon. Nothing more could be said. The seems to be a requirement for tacit inference here. We infer the interior of the tomato. |
| 22413 | Being red simply consists in looking red [McGinn] |
| Full Idea: What we should claim is that being red consists in looking red. | |
| From: Colin McGinn (Subjective View: sec qualities and indexicals [1983], 2) | |
| A reaction: A very nice simple account. There is more to being square than looking square (which may not even guarantee that it is square). That's the primary/secondary distinction in a nut shell. But red things don't look red in the dark. Sufficient, not necessary. |
| 22415 | Relativity means differing secondary perceptions are not real disagreements [McGinn] |
| Full Idea: Relativity permits differences in the perceived secondary qualities not to imply genuine disagreement, whereas perceived differences of primary qualities imply that at least one perceiver is in error. | |
| From: Colin McGinn (Subjective View: sec qualities and indexicals [1983], 2) | |
| A reaction: An example of 'relativity' is colour blindness. Sounds good, but what of one perceiver seeing a square as square, and another seeing it obliquely as a parallelogram? The squareness then seems more like a theory than a perception. |
| 22416 | Phenomenalism is correct for secondary qualities, so scepticism is there impossible [McGinn] |
| Full Idea: We might say that scepticism is ruled out for secondary qualities because (roughly) phenomenalism is correct for them; but phenomenalism is not similarly correct for primary qualities, and scepticism cannot get a foothold. | |
| From: Colin McGinn (Subjective View: sec qualities and indexicals [1983], 2) | |
| A reaction: An odd idea, if phenomenalism says that reality consists entirely of phenomena. I should think phenomenalism is a commitment to the absence of primary qualities. |
| 22422 | Maybe all possible sense experience must involve both secondary and primary qualities [McGinn] |
| Full Idea: The inseparability thesis about perception says that for any actual and possible sense the content of experiences delivered by that sense must be both of secondary qualities and of primary qualities. | |
| From: Colin McGinn (Subjective View: sec qualities and indexicals [1983], 6) | |
| A reaction: That would mean that all possible experience must have a mode of presentation, and also must be 'of' something independent of experience. So a yellow after-image would not count as an 'experience'? |
| 22428 | You understood being red if you know the experience involved; not so with thngs being square [McGinn] |
| Full Idea: To grasp what it is to be red is to know the kind of sensory experience red things produce; ...but it is not true that to grasp what it is to be square one needs to know what kinds of sensory experience square things produce. | |
| From: Colin McGinn (Subjective View: sec qualities and indexicals [1983], 8) | |
| A reaction: Are any experiences involved in the understanding of squareness? We don't know squareness by a priori intuition (do we?). To grasp squareness if may be necessary to have a variety of experiences of it. Or to grasp that it is primary. |
| 22414 | You don't need to know how a square thing looks or feels to understand squareness [McGinn] |
| Full Idea: To grasp what it is for something to be square it is not constitutively necessary to know how square things look or feel, since what it is to be square does not involve any such relation to experience. | |
| From: Colin McGinn (Subjective View: sec qualities and indexicals [1983], 2) | |
| A reaction: You could even describe squareness verbally, unlike redness. It seems crucial that almost any sense (such as bat echoes) can communicate primary qualities, but secondary qualities are tied to a sense, and wouldn't exist without it. |
| 22423 | Touch doesn't provide direct experience of primary qualities, because touch feels temperature [McGinn] |
| Full Idea: Bennett's claim that touch provides experience of primary qualities without experience of any secondary qualities strikes me as false, because tactile experience includes felt temperature, which is a dispositional secondary quality. | |
| From: Colin McGinn (Subjective View: sec qualities and indexicals [1983], 6) | |
| A reaction: [J.Bennett 1971 pp. 90-4] Fair point. What about shape and texture? We experience forces, but the shape is assembled in imagination rather than in experience. So do we meet primary qualities directly in forces, such as acceleration? No secondary quality? |
| 22426 | We can perceive objectively, because primary qualities are not mind-created [McGinn] |
| Full Idea: I hold that experience succeeds in representing the world objectively, since primary quality perceptual content is not contributed by the mind. | |
| From: Colin McGinn (Subjective View: sec qualities and indexicals [1983], 6) | |
| A reaction: My new example of a direct perception of a primary quality is acceleration in a lift. What would we say to one passenger who denied feeling the acceleration? It took an effort to see that mind contributes to secondary qualities (so make more effort?). |
| 22412 | Lockean secondary qualities (unlike primaries) produce particular sensory experiences [McGinn] |
| Full Idea: In the Lockean tradition, secondary qualities are defined as those whose instantiation in an object consists in a power or disposition of the object to produce sensory experiences in perceivers of a certain phenomenological character. | |
| From: Colin McGinn (Subjective View: sec qualities and indexicals [1983], 2) | |
| A reaction: Primary qualities are said to lack such dispositions. Not sure about these definitions. Primaries offer no experiences? With these definitions, comparing them would be a category mistake. I take it primaries reflect reality and secondaries do not. |
| 22421 | Could there be a mind which lacked secondary quality perception? [McGinn] |
| Full Idea: Can we form a conception of a type of mind whose representations are free of secondary quality perceptions? | |
| From: Colin McGinn (Subjective View: sec qualities and indexicals [1983], 6) | |
| A reaction: Nice question. Minds must have experiences, and there has to be a 'way' or 'mode' for those experiences. A mind which directly grasped the primary quality of sphericity would seem to be visionary rather than sensual or experiential. |
| 22424 | Secondary qualities contain information; their variety would be superfluous otherwise [McGinn] |
| Full Idea: Surely we learn something about an object when we discover its secondary qualities? ...If secondary quality experience were informationally inert, its variety would be something of a puzzle. Why not employ the same medium for all primary informaton? | |
| From: Colin McGinn (Subjective View: sec qualities and indexicals [1983], 6) | |
| A reaction: This is important. We can't just focus on the primary qualities, and ignore the secondary. But diverse colours draw attention to information, which can then be translated into neutral data, as in spectroscopic analysis. Locke agrees with this. |
| 22425 | The utility theory says secondary qualities give information useful to human beings [McGinn] |
| Full Idea: Secondary quality perception, according to the utility theory, gives information about the relation between the perceptual object and the perceiver's needs and interests. | |
| From: Colin McGinn (Subjective View: sec qualities and indexicals [1983], 6) | |
| A reaction: Almost the only example I can think of is whether fruit is ripe or rotten. ...Also 'bad' smells. We recognise aggressive animal noises, but that is not the same as dangerous (e.g. rustling snake). Divine design is behind this theory, I think. |
| 7629 | We see objects 'directly' by representing them [McGinn] |
| Full Idea: My view is that we see objects 'directly' by representing them in visual experience. | |
| From: Colin McGinn (Subjective View: sec qualities and indexicals [1983], Ch.8 n1) | |
| A reaction: [Quoted by Maund] This rejects both inference in perception and sense-data, while retaining the notion of representation. It is a view which has gained a lot of support. But how can it be direct if it represents? Photographs can't do that. |
| 3978 | Associations are held to connect Ideas together in the way the world is connected together [Fodor] |
| Full Idea: The laws of associations were held to explicate the semantic coherence of intentional processes, which adjust the causal relations among Ideas to reflect corresponding relations among the things that they're ideas of. | |
| From: Jerry A. Fodor (Jerry A. Fodor on himself [1994], p.296) | |
| A reaction: With the support of evolution, and the backing of a correspondence theory of truth, plus more sophistication in the associations, this might work. |
| 3976 | Intentional science needs objects with semantic and causal properties, and which obey laws [Fodor] |
| Full Idea: If there is to be an intentional science, there must be semantically evaluable things which have causal powers, and there must be laws relating beliefs and desires to one another, and to actions. | |
| From: Jerry A. Fodor (Jerry A. Fodor on himself [1994], p.293) | |
| A reaction: The semantics and causation sound fair enough, but the prospect of finding laws looks bleak (though, contrary to Davidson, I don't see why they can't exist). |
| 3980 | Intentional states and processes may be causal relations among mental symbols [Fodor] |
| Full Idea: It may be that intentional states are relations to mental symbols, and mental processes are implemented by causal relations among these symbols. | |
| From: Jerry A. Fodor (Jerry A. Fodor on himself [1994], p.296) | |
| A reaction: It is hard to see how something could have causal powers just by being a symbol. The theory needs something else to drive the causation. |
| 3981 | Most psychological properties seem to be multiply realisable [Fodor] |
| Full Idea: These days most philosophers of mind suppose that most psychological properties are multiply realisable. | |
| From: Jerry A. Fodor (Jerry A. Fodor on himself [1994], p.298) | |
| A reaction: This is just speculation. The physical part may seem very different, but turn out to be identical in the ways that matter (like a knife made of two different metals). |
| 3975 | Folk psychology explains behaviour by reference to intentional states like belief and desire [Fodor] |
| Full Idea: Folk psychology is primarily intentional explanation; it's the idea that people's behaviour can be explained by reference to the contents of their beliefs and desires. | |
| From: Jerry A. Fodor (Jerry A. Fodor on himself [1994], p.292) | |
| A reaction: Sounds good. To reject folk psychology (as reductivists tend to) is to reject the existence of significant intentional states which have causal properties |
| 22420 | The indexical perspective is subjective, incorrigible and constant [McGinn] |
| Full Idea: I attribute three properties to the indexical perspective: it is subjective, incorrigible, and constant. | |
| From: Colin McGinn (Subjective View: sec qualities and indexicals [1983], 5) | |
| A reaction: That is as good an idea as any for summarising the view (associated with John Perry) that the indexical perspective is an indispensable feature of reality. For a good attack on this, which I favour, see Cappelen and Dever. |
| 18410 | Indexical thought is in relation to my self-consciousness [McGinn] |
| Full Idea: Very roughly, we can say that to think of something indexically is to think of it in relation to me, as I am presented to myself in self-consciousness. | |
| From: Colin McGinn (Subjective View: sec qualities and indexicals [1983], 2) | |
| A reaction: So it is characterised relationally, which doesn't mean it has a distinctive intrinsic character. If I'm lost, and I overhear someone say 'Peter is in Hazlemere', I get the same relational information (in a different mode) without the indexicality. |
| 22417 | Indexicals do not figure in theories of physics, because they are not explanatory causes [McGinn] |
| Full Idea: Indexicals are like secondary qualities in not figuring in causal explanations of the interactions of objects: physics omits them not because they are relative and egocentric, but because they do not constitute explanatory predicates of a causal theory. | |
| From: Colin McGinn (Subjective View: sec qualities and indexicals [1983], 2) | |
| A reaction: They are outside explanatory physics, but not outside explanation. The object moved because a force acted on it; or the object moved because I wanted it moved. |
| 18402 | Indexical concepts are indispensable, as we need them for the power to act [McGinn] |
| Full Idea: The present suggestion is that indexical concepts are ineliminable because without them agency would be impossible: when I imagine myself divested of indexical thoughts employing only centreless mental representations, I am deprived of the power to act. | |
| From: Colin McGinn (Subjective View: sec qualities and indexicals [1983], 6) | |
| A reaction: A nice clear statement of the view developed by Perry and Lewis. I agree with Cappelen and Dever that it is entirely wrong, and that indexical thought is entirely eliminable, and nothing special. |
| 3982 | How could the extrinsic properties of thoughts supervene on their intrinsic properties? [Fodor] |
| Full Idea: It is hard to see how the extrinsic properties of thoughts could supervene on their intrinsic properties. | |
| From: Jerry A. Fodor (Jerry A. Fodor on himself [1994], p.299) | |
| A reaction: This doesn't seem a big problem. Sometimes represented experiences establish the match; sometimes the match is not very good, or even wrong. |
| 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. |
| 22418 | I can know indexical truths a priori, unlike their non-indexical paraphrases [McGinn] |
| Full Idea: I know the truth of the sentence 'I am here now' a priori, but I do not know a priori 'McGinn is in London on 15th Nov 1981'. | |
| From: Colin McGinn (Subjective View: sec qualities and indexicals [1983], 3) | |
| A reaction: I'm not convinced that I can grasp the concepts of 'here' and 'now' (i.e. space and time) by purely a priori means. But he certainly shows that you can't glibly dismiss indexicals by paraphrasing them in that way. |
| 3977 | Laws are true generalisations which support counterfactuals and are confirmed by instances [Fodor] |
| Full Idea: Laws are true generalisations that support counterfactuals and are confirmed by their instances. | |
| From: Jerry A. Fodor (Jerry A. Fodor on himself [1994], p.293) | |
| A reaction: This seems correct, but it doesn't disentangle laws as mental states from laws as features of nature |
| 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'. |