18 ideas
21959 | Metaphysics is the most general attempt to make sense of things [Moore,AW] |
Full Idea: Metaphysics is the most general attempt to make sense of things. | |
From: A.W. Moore (The Evolution of Modern Metaphysics [2012], Intro) | |
A reaction: This is the first sentence of Moore's book, and a touchstone idea all the way through. It stands up well, because it says enough without committing to too much. I have to agree with it. It implies explanation as the key. I like generality too. |
9978 | Analytic philosophy focuses too much on forms of expression, instead of what is actually said [Tait] |
Full Idea: The tendency to attack forms of expression rather than attempting to appreciate what is actually being said is one of the more unfortunate habits that analytic philosophy inherited from Frege. | |
From: William W. Tait (Frege versus Cantor and Dedekind [1996], IV) | |
A reaction: The key to this, I say, is to acknowledge the existence of propositions (in brains). For example, this belief will make teachers more sympathetic to pupils who are struggling to express an idea, and verbal nit-picking becomes totally irrelevant. |
9986 | The null set was doubted, because numbering seemed to require 'units' [Tait] |
Full Idea: The conception that what can be numbered is some object (including flocks of sheep) relative to a partition - a choice of unit - survived even in the late nineteenth century in the form of the rejection of the null set (and difficulties with unit sets). | |
From: William W. Tait (Frege versus Cantor and Dedekind [1996], IX) | |
A reaction: This old view can't be entirely wrong! Frege makes the point that if asked to count a pack of cards, you must decide whether to count cards, or suits, or pips. You may not need a 'unit', but you need a concept. 'Units' name concept-extensions nicely! |
9984 | We can have a series with identical members [Tait] |
Full Idea: Why can't we have a series (as opposed to a linearly ordered set) all of whose members are identical, such as (a, a, a...,a)? | |
From: William W. Tait (Frege versus Cantor and Dedekind [1996], VII) | |
A reaction: The question is whether the items order themselves, which presumably the natural numbers are supposed to do, or whether we impose the order (and length) of the series. What decides how many a's there are? Do we order, or does nature? |
13416 | Mathematics must be based on axioms, which are true because they are axioms, not vice versa [Tait, by Parsons,C] |
Full Idea: The axiomatic conception of mathematics is the only viable one. ...But they are true because they are axioms, in contrast to the view advanced by Frege (to Hilbert) that to be a candidate for axiomhood a statement must be true. | |
From: report of William W. Tait (Intro to 'Provenance of Pure Reason' [2005], p.4) by Charles Parsons - Review of Tait 'Provenance of Pure Reason' §2 | |
A reaction: This looks like the classic twentieth century shift in the attitude to axioms. The Greek idea is that they must be self-evident truths, but the Tait-style view is that they are just the first steps in establishing a logical structure. I prefer the Greeks. |
1507 | We don't have time for infinite quantity, but we do for infinite divisibility, because time is also divisible [Aristotle on Zeno of Elea] |
Full Idea: Although it is impossible to make contact in a finite time with things that are infinite in quantity, it is possible to do so with things that are infinitely divisible, since the time itself is also infinite in this way. | |
From: comment on Zeno (Elea) (fragments/reports [c.450 BCE], A25) by Aristotle - Physics 233a21 |
5109 | The fast runner must always reach the point from which the slower runner started [Zeno of Elea, by Aristotle] |
Full Idea: Zeno's so-called 'Achilles' claims that the slowest runner will never be caught by the fastest runner, because the one behind has first to reach the point from which the one in front started, and so the slower one is bound always to be in front. | |
From: report of Zeno (Elea) (fragments/reports [c.450 BCE]) by Aristotle - Physics 239b14 | |
A reaction: The point is that the slower runner will always have moved on when the faster runner catches up with the starting point. We must understand how humble the early Greeks felt when they confronted arguments like this. It was like a divine revelation. |
1512 | Zeno is wrong that one grain of millet makes a sound; why should one grain achieve what the whole bushel does? [Aristotle on Zeno of Elea] |
Full Idea: Zeno is wrong in arguing that the tiniest fragment of millet makes a sound; there is no reason why the fragment should be able to move in any amount of time the air which the whole bushel moved as it fell. | |
From: comment on Zeno (Elea) (fragments/reports [c.450 BCE], A29) by Aristotle - Physics 250a16 |
1508 | Zeno's arrow paradox depends on the assumption that time is composed of nows [Aristotle on Zeno of Elea] |
Full Idea: Zeno's third argument claims that a moving arrow is still. Here the conclusion depends on assuming that time is composed of nows; if this assumption is not granted, the argument fails. | |
From: comment on Zeno (Elea) (fragments/reports [c.450 BCE], A27?) by Aristotle - Physics 239b5 |
21958 | Appearances are nothing beyond representations, which is transcendental ideality [Moore,AW] |
Full Idea: Appearances in general are nothing outside our representations, which is just what we mean by transcendental ideality. | |
From: A.W. Moore (The Evolution of Modern Metaphysics [2012], B535/A507) |
9981 | Abstraction is 'logical' if the sense and truth of the abstraction depend on the concrete [Tait] |
Full Idea: If the sense of a proposition about the abstract domain is given in terms of the corresponding proposition about the (relatively) concrete domain, ..and the truth of the former is founded upon the truth of the latter, then this is 'logical abstraction'. | |
From: William W. Tait (Frege versus Cantor and Dedekind [1996], V) | |
A reaction: The 'relatively' in parentheses allows us to apply his idea to levels of abstraction, and not just to the simple jump up from the concrete. I think Tait's proposal is excellent, rather than purloining 'abstraction' for an internal concept within logic. |
9982 | Cantor and Dedekind use abstraction to fix grammar and objects, not to carry out proofs [Tait] |
Full Idea: Although (in Cantor and Dedekind) abstraction does not (as has often been observed) play any role in their proofs, but it does play a role, in that it fixes the grammar, the domain of meaningful propositions, and so determining the objects in the proofs. | |
From: William W. Tait (Frege versus Cantor and Dedekind [1996], V) | |
A reaction: [compressed] This is part of a defence of abstractionism in Cantor and Dedekind (see K.Fine also on the subject). To know the members of a set, or size of a domain, you need to know the process or function which created the set. |
9985 | Abstraction may concern the individuation of the set itself, not its elements [Tait] |
Full Idea: A different reading of abstraction is that it concerns, not the individuating properties of the elements relative to one another, but rather the individuating properties of the set itself, for example the concept of what is its extension. | |
From: William W. Tait (Frege versus Cantor and Dedekind [1996], VIII) | |
A reaction: If the set was 'objects in the room next door', we would not be able to abstract from the objects, but we might get to the idea of things being contain in things, or the concept of an object, or a room. Wrong. That's because they are objects... Hm. |
9972 | Why should abstraction from two equipollent sets lead to the same set of 'pure units'? [Tait] |
Full Idea: Why should abstraction from two equipollent sets lead to the same set of 'pure units'? | |
From: William W. Tait (Frege versus Cantor and Dedekind [1996]) | |
A reaction: [Tait is criticising Cantor] This expresses rather better than Frege or Dummett the central problem with the abstractionist view of how numbers are derived from matching groups of objects. |
9980 | If abstraction produces power sets, their identity should imply identity of the originals [Tait] |
Full Idea: If the power |A| is obtained by abstraction from set A, then if A is equipollent to set B, then |A| = |B|. But this does not imply that A = B. So |A| cannot just be A, taken in abstraction, unless that can identify distinct sets, ..or create new objects. | |
From: William W. Tait (Frege versus Cantor and Dedekind [1996], V) | |
A reaction: An elegant piece of argument, which shows rather crucial facts about abstraction. We are then obliged to ask how abstraction can create an object or a set, if the central activity of abstraction is just ignoring certain features. |
454 | If there are many things they must have a finite number, but there must be endless things between them [Zeno of Elea] |
Full Idea: It things are many, they can't be more or less than they are, so they must be finite, but also there must be endless things between each thing, so they must be infinite. | |
From: Zeno (Elea) (fragments/reports [c.450 BCE], B3), quoted by Simplicius - On Aristotle's 'Physics' 140.29 |
455 | That which moves, moves neither in the place in which it is, nor in that in which it is not [Zeno of Elea] |
Full Idea: That which moves, moves neither in the place in which it is, nor in that in which it is not. | |
From: Zeno (Elea) (fragments/reports [c.450 BCE], B4), quoted by (who?) - where? |
1511 | If everything is in a place, what is the place in? Place doesn't exist [Zeno of Elea, by Simplicius] |
Full Idea: If there is a place it will be in something, because everything that exists is in something. But what is in something is in a place. Therefore the place will be in a place, and so on ad infinitum. Therefore, there is no such thing as place. | |
From: report of Zeno (Elea) (fragments/reports [c.450 BCE], B3) by Simplicius - On Aristotle's 'Physics' 9.562.3 |