48 ideas
9901 | Numbers can't be sets if there is no agreement on which sets they are [Benacerraf] |
Full Idea: The fact that Zermelo and Von Neumann disagree on which particular sets the numbers are is fatal to the view that each number is some particular set. | |
From: Paul Benacerraf (What Numbers Could Not Be [1965], II) | |
A reaction: I agree. A brilliantly simple argument. There is the possibility that one of the two accounts is correct (I would vote for Zermelo), but it is not actually possible to prove it. |
9912 | There are no such things as numbers [Benacerraf] |
Full Idea: There are no such things as numbers. | |
From: Paul Benacerraf (What Numbers Could Not Be [1965], IIIC) | |
A reaction: Mill said precisely the same (Idea 9794). I think I agree. There has been a classic error of reification. An abstract pattern is not an object. If I coin a word for all the three-digit numbers in our system, I haven't created a new 'object'. |
9151 | Benacerraf says numbers are defined by their natural ordering [Benacerraf, by Fine,K] |
Full Idea: Benacerraf thinks of numbers as being defined by their natural ordering. | |
From: report of Paul Benacerraf (What Numbers Could Not Be [1965]) by Kit Fine - Cantorian Abstraction: Recon. and Defence §5 | |
A reaction: My intuition is that cardinality is logically prior to ordinality, since that connects better with the experienced physical world of objects. Just as the fact that people have different heights must precede them being arranged in height order. |
13891 | To understand finite cardinals, it is necessary and sufficient to understand progressions [Benacerraf, by Wright,C] |
Full Idea: Benacerraf claims that the concept of a progression is in some way the fundamental arithmetical notion, essential to understanding the idea of a finite cardinal, with a grasp of progressions sufficing for grasping finite cardinals. | |
From: report of Paul Benacerraf (What Numbers Could Not Be [1965]) by Crispin Wright - Frege's Concept of Numbers as Objects 3.xv | |
A reaction: He cites Dedekind (and hence the Peano Axioms) as the source of this. The interest is that progression seems to be fundamental to ordianls, but this claims it is also fundamental to cardinals. Note that in the first instance they are finite. |
17904 | A set has k members if it one-one corresponds with the numbers less than or equal to k [Benacerraf] |
Full Idea: Any set has k members if and only if it can be put into one-to-one correspondence with the set of numbers less than or equal to k. | |
From: Paul Benacerraf (What Numbers Could Not Be [1965], I) | |
A reaction: This is 'Ernie's' view of things in the paper. This defines the finite cardinal numbers in terms of the finite ordinal numbers. He has already said that the set of numbers is well-ordered. |
17906 | To explain numbers you must also explain cardinality, the counting of things [Benacerraf] |
Full Idea: I would disagree with Quine. The explanation of cardinality - i.e. of the use of numbers for 'transitive counting', as I have called it - is part and parcel of the explication of number. | |
From: Paul Benacerraf (What Numbers Could Not Be [1965], I n2) | |
A reaction: Quine says numbers are just a progression, with transitive counting as a bonus. Interesting that Benacerraf identifies cardinality with transitive counting. I would have thought it was the possession of numerical quantity, not ascertaining it. |
9898 | We can count intransitively (reciting numbers) without understanding transitive counting of items [Benacerraf] |
Full Idea: Learning number words in the right order is counting 'intransitively'; using them as measures of sets is counting 'transitively'. ..It seems possible for someone to learn the former without learning the latter. | |
From: Paul Benacerraf (What Numbers Could Not Be [1965], I) | |
A reaction: Scruton's nice question (Idea 3907) is whether you could be said to understand numbers if you could only count intransitively. I would have thought such a state contained no understanding at all of numbers. Benacerraf agrees. |
17903 | Someone can recite numbers but not know how to count things; but not vice versa [Benacerraf] |
Full Idea: It seems that it is possible for someone to learn to count intransitively without learning to count transitively. But not vice versa. | |
From: Paul Benacerraf (What Numbers Could Not Be [1965], I) | |
A reaction: Benacerraf favours the priority of the ordinals. It is doubtful whether you have grasped cardinality properly if you don't know how to count things. Could I understand 'he has 27 sheep', without understanding the system of natural numbers? |
9897 | The application of a system of numbers is counting and measurement [Benacerraf] |
Full Idea: The application of a system of numbers is counting and measurement. | |
From: Paul Benacerraf (What Numbers Could Not Be [1965], I) | |
A reaction: A simple point, but it needs spelling out. Counting seems prior, in experience if not in logic. Measuring is a luxury you find you can indulge in (by imagining your quantity) split into parts, once you have mastered counting. |
9900 | For Zermelo 3 belongs to 17, but for Von Neumann it does not [Benacerraf] |
Full Idea: Ernie's number progression is [φ],[φ,[φ]],[φ,[φ],[φ,[φ,[φ]]],..., whereas Johnny's is [φ],[[φ]],[[[φ]]],... For Ernie 3 belongs to 17, not for Johnny. For Ernie 17 has 17 members; for Johnny it has one. | |
From: Paul Benacerraf (What Numbers Could Not Be [1965], II) | |
A reaction: Benacerraf's point is that there is no proof-theoretic way to choose between them, though I am willing to offer my intuition that Ernie (Zermelo) gives the right account. Seventeen pebbles 'contains' three pebbles; you must pass 3 to count to 17. |
9899 | The successor of x is either x and all its members, or just the unit set of x [Benacerraf] |
Full Idea: For Ernie, the successor of a number x was the set consisting of x and all the members of x, while for Johnny the successor of x was simply [x], the unit set of x - the set whose only member is x. | |
From: Paul Benacerraf (What Numbers Could Not Be [1965], II) | |
A reaction: See also Idea 9900. Benacerraf's famous point is that it doesn't seem to make any difference to arithmetic which version of set theory you choose as its basis. I take this to conclusively refute the idea that numbers ARE sets. |
8697 | Disputes about mathematical objects seem irrelevant, and mathematicians cannot resolve them [Benacerraf, by Friend] |
Full Idea: If two children were brought up knowing two different set theories, they could entirely agree on how to do arithmetic, up to the point where they discuss ontology. There is no mathematical way to tell which is the true representation of numbers. | |
From: report of Paul Benacerraf (What Numbers Could Not Be [1965]) by Michèle Friend - Introducing the Philosophy of Mathematics | |
A reaction: Benacerraf ends by proposing a structuralist approach. If mathematics is consistent with conflicting set theories, then those theories are not shedding light on mathematics. |
8304 | No particular pair of sets can tell us what 'two' is, just by one-to-one correlation [Benacerraf, by Lowe] |
Full Idea: Hume's Principle can't tell us what a cardinal number is (this is one lesson of Benacerraf's well-known problem). An infinity of pairs of sets could actually be the number two (not just the simplest sets). | |
From: report of Paul Benacerraf (What Numbers Could Not Be [1965]) by E.J. Lowe - The Possibility of Metaphysics 10.3 | |
A reaction: The drift here is for numbers to end up as being basic, axiomatic, indefinable, universal entities. Since I favour patterns as the basis of numbers, I think the basis might be in a pre-verbal experience, which even a bird might have, viewing its eggs. |
9906 | If ordinal numbers are 'reducible to' some set-theory, then which is which? [Benacerraf] |
Full Idea: If a particular set-theory is in a strong sense 'reducible to' the theory of ordinal numbers... then we can still ask, but which is really which? | |
From: Paul Benacerraf (What Numbers Could Not Be [1965], IIIB) | |
A reaction: A nice question about all reductions. If we reduce mind to brain, does that mean that brain is really just mind. To have a direction (up/down?), reduction must lead to explanation in a single direction only. Do numbers explain sets? |
9907 | If any recursive sequence will explain ordinals, then it seems to be the structure which matters [Benacerraf] |
Full Idea: If any recursive sequence whatever would do to explain ordinal numbers suggests that what is important is not the individuality of each element, but the structure which they jointly exhibit. | |
From: Paul Benacerraf (What Numbers Could Not Be [1965], IIIC) | |
A reaction: This sentence launched the whole modern theory of Structuralism in mathematics. It is hard to see what properties a number-as-object could have which would entail its place in an ordinal sequence. |
9908 | The job is done by the whole system of numbers, so numbers are not objects [Benacerraf] |
Full Idea: 'Objects' do not do the job of numbers singly; the whole system performs the job or nothing does. I therefore argue that numbers could not be objects at all. | |
From: Paul Benacerraf (What Numbers Could Not Be [1965], IIIC) | |
A reaction: This thought is explored by structuralism - though it is a moot point where mere 'nodes' in a system (perhaps filled with old bits of furniture) will do the job either. No one ever explains the 'power' of numbers (felt when you do a sudoku). Causal? |
9909 | The number 3 defines the role of being third in a progression [Benacerraf] |
Full Idea: Any object can play the role of 3; that is, any object can be the third element in some progression. What is peculiar to 3 is that it defines that role, not by being a paradigm, but by representing the relation of any third member of a progression. | |
From: Paul Benacerraf (What Numbers Could Not Be [1965], IIIC) | |
A reaction: An interesting early attempt to spell out the structuralist idea. I'm thinking that the role is spelled out by the intersection of patterns which involve threes. |
9911 | Number words no more have referents than do the parts of a ruler [Benacerraf] |
Full Idea: Questions of the identification of the referents of number words should be dismissed as misguided in just the way that a question about the referents of the parts of a ruler would be seen as misguided. | |
From: Paul Benacerraf (What Numbers Could Not Be [1965], IIIC) | |
A reaction: What a very nice simple point. It would be very strange to insist that every single part of the continuum of a ruler should be regarded as an 'object'. |
8925 | Mathematical objects only have properties relating them to other 'elements' of the same structure [Benacerraf] |
Full Idea: Mathematical objects have no properties other than those relating them to other 'elements' of the same structure. | |
From: Paul Benacerraf (What Numbers Could Not Be [1965], p.285), quoted by Fraser MacBride - Structuralism Reconsidered §3 n13 | |
A reaction: Suppose we only had one number - 13 - and we all cried with joy when we recognised it in a group of objects. Would that be a number, or just a pattern, or something hovering between the two? |
9938 | How can numbers be objects if order is their only property? [Benacerraf, by Putnam] |
Full Idea: Benacerraf raises the question how numbers can be 'objects' if they have no properties except order in a particular ω-sequence. | |
From: report of Paul Benacerraf (What Numbers Could Not Be [1965], p.301) by Hilary Putnam - Mathematics without Foundations | |
A reaction: Frege certainly didn't think that order was their only property (see his 'borehole' metaphor in Grundlagen). It might be better to say that they are objects which only have relational properties. |
9910 | Number-as-objects works wholesale, but fails utterly object by object [Benacerraf] |
Full Idea: The identification of numbers with objects works wholesale but fails utterly object by object. | |
From: Paul Benacerraf (What Numbers Could Not Be [1965], IIIC) | |
A reaction: This seems to be a glaring problem for platonists. You can stare at 1728 till you are blue in the face, but it only begins to have any properties at all once you examine its place in the system. This is unusual behaviour for an object. |
9903 | Number words are not predicates, as they function very differently from adjectives [Benacerraf] |
Full Idea: The unpredicative nature of number words can be seen by noting how different they are from, say, ordinary adjectives, which do function as predicates. | |
From: Paul Benacerraf (What Numbers Could Not Be [1965], II) | |
A reaction: He points out that 'x is seventeen' is a rare construction in English, unlike 'x is happy/green/interesting', and that numbers outrank all other adjectives (having to appear first in any string of them). |
9904 | The set-theory paradoxes mean that 17 can't be the class of all classes with 17 members [Benacerraf] |
Full Idea: In no consistent theory is there a class of all classes with seventeen members. The existence of the paradoxes is a good reason to deny to 'seventeen' this univocal role of designating the class of all classes with seventeen members. | |
From: Paul Benacerraf (What Numbers Could Not Be [1965], II) | |
A reaction: This was Frege's disaster, and seems to block any attempt to achieve logicism by translating numbers into sets. It now seems unclear whether set theory is logic, or mathematics, or sui generis. |
16588 | I prefer a lack of form to mean non-existence, than to think of some quasi-existence [Augustine] |
Full Idea: I sooner judged that what lacks all form does not exist, than thought of as something in between form and nothing, neither formed nor nothing, unformed and next to nothing. | |
From: Augustine (Confessions [c.398], XII.6), quoted by Robert Pasnau - Metaphysical Themes 1274-1671 03.1 | |
A reaction: Scholastics were struck by the contrast between this remark, and the remark of Averroes (Idea 16587) that prime matter was halfway existence. Their two great authorities disagreed! This sort of thing stimulated the revival of metaphysics. |
22979 | Three main questions seem to be whether a thing is, what it is, and what sort it is [Augustine] |
Full Idea: I am told that I can ask three sorts of questions - whether a thing is, what it is, and what sort it is. | |
From: Augustine (Confessions [c.398], X.10) | |
A reaction: This seems to be a very Aristotelian approach. I am pleased to see that what it is and what sort it is are not conflated. The first one must be its individual essence, and the second its generic essence. |
9905 | Identity statements make sense only if there are possible individuating conditions [Benacerraf] |
Full Idea: Identity statements make sense only in contexts where there exist possible individuating conditions. | |
From: Paul Benacerraf (What Numbers Could Not Be [1965], III) | |
A reaction: He is objecting to bizarre identifications involving numbers. An identity statement may be bizarre even if we can clearly individuate the two candidates. Winston Churchill is a Mars Bar. Identifying George Orwell with Eric Blair doesn't need a 'respect'. |
22977 | I can distinguish different smells even when I am not experiencing them [Augustine] |
Full Idea: I can distinguish the scent of lilies from that of violets, even though there is no scent at all in my nostrils. | |
From: Augustine (Confessions [c.398], X.08) | |
A reaction: Augustine has a nice introspective account of how we experience memory, and identifies lots of puzzling features. I know I can identify the smell of vinegar, but I can't bring it to mind, the way I can the appearance of roses. |
22981 | Mind and memory are the same, as shown in 'bear it in mind' or 'it slipped from mind' [Augustine] |
Full Idea: The mind and the memory are one and the same. We even call the memory the mind, for when we tell a person to remember something, we tell them to 'bear this in mind', and when we forget something 'it slipped out of my mind'. | |
From: Augustine (Confessions [c.398], X.14) | |
A reaction: This idea has become familiar in modern neuroscience, I think, presumably because we do not find distinct types of neurons for consciousness and for memory. |
22980 | Memory contains innumerable principles of maths, as well as past sense experiences [Augustine] |
Full Idea: The memory contains the innumerable principles and laws of numbers and dimensions. None of these can have been conveyed to me by the bodily senses. | |
From: Augustine (Confessions [c.398], X.12) | |
A reaction: Even if you have a fairly empirical view of the sources of mathematics (a view with which I sympathise), it must by admitted that our endless extrapolations from the sources also reside in memory. So we remember thoughts as well as experiences. |
22982 | Why does joy in my mind make me happy, but joy in my memory doesn't? [Augustine] |
Full Idea: How can it be that my mind can be happy because of the joy that is in it, and yet my memory is not sad by reason of the sadness that is in it? | |
From: Augustine (Confessions [c.398], X.14) | |
A reaction: This seems to contradict his thought in Idea 22981, that memory and mind are the same. Recall seems to be a part of consciousness which is not fully wired up to the rest of the mind. |
22983 | We would avoid remembering sorrow or fear if that triggered the emotions afresh [Augustine] |
Full Idea: If we had to experience sorrow or fear every time that we mentioned these emotions, no one would be willing to speak of them. | |
From: Augustine (Confessions [c.398], X.14) | |
A reaction: Remembering the death of a loved one can trigger fresh grief, but remembering their dangerous illness from which they recovered no longer contains the feeling of fear. |
22978 | Memory is so vast that I cannot recognise it as part of my mind [Augustine] |
Full Idea: The memory is a vast immeasurable sanctuary. It is part of my nature, but I cannot understand all that I am. Hence the mind is too narrow to contain itself entirely. Is the other part outside of itself, and not within it? How then can it be a part? | |
From: Augustine (Confessions [c.398], X.08) | |
A reaction: He seems to understand the mind as entirely consisting of consciousness. Nevertheless, this seems to be the first inklings of the modern externalist view of the mind. |
22984 | Without memory I could not even speak of myself [Augustine] |
Full Idea: I do not understand the power of memory that is in myself, although without it I could not even speak of myself. | |
From: Augustine (Confessions [c.398], X.16) | |
A reaction: Even if the self is not identical with memory, this idea seems to establish that memory is an essential aspect of the self. This point is neglected by those who see the self as an entity (the 'soul pearl') which persists through all experience. |
5982 | If the future does not exist, how can prophets see it? [Augustine] |
Full Idea: How do prophets see the future, if there is not a future to be seen? | |
From: Augustine (Confessions [c.398], XI.17) | |
A reaction: The answer, I suspect, is that prophets can't see the future. The prospect that the future already exists would seem to saboutage human freedom and responsibility, and point to Calvinist predestination, and even fatalism. |
22976 | Memories are preserved separately, according to category [Augustine] |
Full Idea: In memory everything is preserved separately, according to its category. | |
From: Augustine (Confessions [c.398], X.08) | |
A reaction: This strikes me as the first seeds of the idea that the mind functions by means of mental files. Our memories of cats are 'close to' or 'linked to' our memories of dogs. |
22985 | Everyone wants happiness [Augustine] |
Full Idea: Surely happiness is what everyone wants, so much so that there can be none who do not want it? | |
From: Augustine (Confessions [c.398], X.20) | |
A reaction: His concept of happiness is, of course, religious. Occasionally you meet habitual grumblers about life who give the impression that they are only happy when they are discontented. So happiness is achieving desires, not feeling good? |
22439 | There are only duties if there are rights, so truth is only for those with a right to it [Constant] |
Full Idea: A duty is that on the part of one being which corresponds to the rights of another. Where there are no rights there are no duties. To tell the truth is therefore a duty, but only to the one who has the right to the truth. | |
From: Benjamin Constant (On Political Reactions [1797], p.123), quoted by Immanuel Kant - On a supposed right to lie p.28 | |
A reaction: We can't claim a right to have all questions answered truthfully (because there is a right to privacy), but we might claim a right not to be lied to (as long as we accept a refusal to answer). Kant rejected this idea. |
22440 | Unconditional truth-telling makes a society impossible [Constant] |
Full Idea: The moral principle 'it is a duty to tell the truth' would, if taken unconditionally and singly, make any society impossible. | |
From: Benjamin Constant (On Political Reactions [1797], p.124), quoted by Immanuel Kant - On a supposed right to lie p.28 | |
A reaction: He gives the well known example of the murderer at the door asking if your friend is inside. Compare everyone becoming perfectly telepathic. Our society would collapse, but a new society would learn to live with it. |
5984 | Maybe time is an extension of the mind [Augustine] |
Full Idea: I begin to wonder whether time is an extension of the mind itself. | |
From: Augustine (Confessions [c.398], XI.26) | |
A reaction: The observation that the mind creates a 'specious present' (spreading experience out over a short fraction of second) reinforces this. Personally I like David Marshall's proposal that consciousness is entirely memory, which would deny this idea. |
22888 | To be aware of time it can only exist in the mind, as memory or anticipation [Augustine, by Bardon] |
Full Idea: Augustine answers that for us to be aware of time it must exist only in the mind, …and the difference between past and future is just the difference between memory and anticipation. | |
From: report of Augustine (Confessions [c.398]) by Adrian Bardon - Brief History of the Philosophy of Time 1 'Augustine's' | |
A reaction: This is an extreme idealist view. Are we to say that the past consists only of what can be remembered, and the future only of what is anticipated? Absurd anti-realism, in my view. Where do his concepts come from, asks Le Poidevin. |
5980 | How can ten days ahead be a short time, if it doesn't exist? [Augustine] |
Full Idea: A short time ago or a short time ahead we might put at ten days, but how can anything which does not exist be either long or short? | |
From: Augustine (Confessions [c.398], XI.15) | |
A reaction: A nice question, which gets at the paradoxical nature of time very nicely. How can it be long, but non-existent? We could break the paradox by concluding '..and therefore time does exist', even though we can't see how. |
5979 | If the past is no longer, and the future is not yet, how can they exist? [Augustine] |
Full Idea: Of the three divisions of time, how can two, the past and the future, be, when the past no longer is, and the future is not yet? | |
From: Augustine (Confessions [c.398], XI.14) | |
A reaction: This is the oldest bewilderment about time, which naturally leads us to the thought that time cannot actually 'exist'. The remark implies that at least 'now' is safe, but that also succumbs to paradox pretty quickly. |
5981 | The whole of the current year is not present, so how can it exist? [Augustine] |
Full Idea: We cannot say that the whole of the current year is present, and if the whole of it is not present, the year is not present. | |
From: Augustine (Confessions [c.398], XI.15) | |
A reaction: Another nice way of presenting the paradox of time. We are in a particular year, so it has to be real. |
5978 | I know what time is, until someone asks me to explain it [Augustine] |
Full Idea: I know well enough what time is, provided that nobody asks me; but if I am asked what it is and try to explain, I am baffled. | |
From: Augustine (Confessions [c.398], XI.14) | |
A reaction: A justly famous remark, even though it adds nothing to our knowledge of time. This sort of thought pushes us towards accepting many things as axiomatic, such as time, space, identity, persons, mind. |
5983 | I disagree with the idea that time is nothing but cosmic movement [Augustine] |
Full Idea: I once heard a learned man say that time is nothing but the movement of the sun and the moon and the stars, but I do not agree. | |
From: Augustine (Confessions [c.398], XI.22) | |
A reaction: It is tempting to say that you either take time or movement as axiomatic, and describe one in terms of the other, but you are stuck unable to give the initial statement of the axiom without mentioning the second property you were saving for later. |
5977 | Heaven and earth must be created, because they are subject to change [Augustine] |
Full Idea: The fact that heaven and earth are there proclaims that they were created, for they are subject to change and variation; ..the meaning of change and variation is that something is there which was not there before. | |
From: Augustine (Confessions [c.398], XI.04) | |
A reaction: It seems possible that the underlying matter is eternal (as in various conservation laws, such as that of energy), and that all change is in the form rather than the substance. |
22887 | If God existed before creation, why would a perfect being desire to change things? [Augustine, by Bardon] |
Full Idea: If nothing existed by God before creation, then what could have happened to, or within, God that led God to decide to create the universe at that particular moment? Why would an eternal or perfect being want or need to change? | |
From: report of Augustine (Confessions [c.398]) by Adrian Bardon - Brief History of the Philosophy of Time 1 'Augustine's' | |
A reaction: I suppose you could reply that change is superior to stasis, but then why did God delay the creation? |
5976 | If God is outside time in eternity, can He hear prayers? [Augustine] |
Full Idea: O Lord, since you are outside time in eternity, are you unaware of the things that I tell you? | |
From: Augustine (Confessions [c.398], XI.01) | |
A reaction: This strikes me as the single most difficult and most elusive question about the nature of a supreme divine being. If the being is trapped in time, as we are, it is greatly diminished, and if it is outside, it is hard to see how it could be a participant. |