Combining Philosophers

All the ideas for Karl Weierstrass, Geoffrey Hellman and Nuel D. Belnap

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9 ideas

6. Mathematics / A. Nature of Mathematics / 5. The Infinite / k. Infinitesimals

18086	Weierstrass eliminated talk of infinitesimals [Weierstrass, by Kitcher]
	Full Idea: Weierstrass effectively eliminated the infinitesimalist language of his predecessors.
	From: report of Karl Weierstrass (works [1855]) by Philip Kitcher - The Nature of Mathematical Knowledge 10.6

6. Mathematics / A. Nature of Mathematics / 5. The Infinite / l. Limits

18092	Weierstrass made limits central, but the existence of limits still needed to be proved [Weierstrass, by Bostock]
	Full Idea: After Weierstrass had stressed the importance of limits, one now needed to be able to prove the existence of such limits.
	From: report of Karl Weierstrass (works [1855]) by David Bostock - Philosophy of Mathematics 4.4
	A reaction: The solution to this is found in work on series (going back to Cauchy), and on Dedekind's cuts.

6. Mathematics / B. Foundations for Mathematics / 7. Mathematical Structuralism / a. Structuralism

8921	Structuralism is now common, studying relations, with no regard for what the objects might be [Hellman]
	Full Idea: With developments in modern mathematics, structuralist ideas have become commonplace. We study 'abstract structures', having relations without regard to the objects. As Hilbert famously said, items of furniture would do.
	From: Geoffrey Hellman (Structuralism [2007], §1)
	A reaction: Hilbert is known as a Formalist, which suggests that modern Structuralism is a refined and more naturalist version of the rather austere formalist view. Presumably the sofa can't stand for six, so a structural definition of numbers is needed.

6. Mathematics / B. Foundations for Mathematics / 7. Mathematical Structuralism / c. Nominalist structuralism

8698	Modal structuralism says mathematics studies possible structures, which may or may not be actualised [Hellman, by Friend]
	Full Idea: The modal structuralist thinks of mathematical structures as possibilities. The application of mathematics is just the realisation that a possible structure is actualised. As structures are possibilities, realist ontological problems are avoided.
	From: report of Geoffrey Hellman (Mathematics without Numbers [1989]) by Michèle Friend - Introducing the Philosophy of Mathematics 4.3
	A reaction: Friend criticises this and rejects it, but it is appealing. Mathematics should aim to be applicable to any possible world, and not just the actual one. However, does the actual world 'actualise a mathematical structure'?

9557	Statements of pure mathematics are elliptical for a sort of modal conditional [Hellman, by Chihara]
	Full Idea: Hellman represents statements of pure mathematics as elliptical for modal conditionals of a certain sort.
	From: report of Geoffrey Hellman (Mathematics without Numbers [1989]) by Charles Chihara - A Structural Account of Mathematics 5.3
	A reaction: It's a pity there is such difficulty in understanding conditionals (see Graham Priest on the subject). I intuit a grain of truth in this, though I take maths to reflect the structure of the actual world (with possibilities being part of that world).

10263	Modal structuralism can only judge possibility by 'possible' models [Shapiro on Hellman]
	Full Idea: The usual way to show that a sentence is possible is to show that it has a model, but for Hellman presumably a sentence is possible if it might have a model (or if, possibly, it has a model). It is not clear what this move brings us.
	From: comment on Geoffrey Hellman (Mathematics without Numbers [1989]) by Stewart Shapiro - Philosophy of Mathematics 7.3
	A reaction: I can't assess this, but presumably the possibility of the model must be demonstrated in some way. Aren't all models merely possible, because they are based on axioms, which seem to be no more than possibilities?

8922	Maybe mathematical objects only have structural roles, and no intrinsic nature [Hellman]
	Full Idea: There is the tantalizing possibility that perhaps mathematical objects 'have no nature' at all, beyond their 'structural role'.
	From: Geoffrey Hellman (Structuralism [2007], §1)
	A reaction: This would fit with a number being a function rather than an object. We are interested in what cars do, not the bolts that hold them together? But the ontology of mathematics is quite separate from how you do mathematics.

14. Science / C. Induction / 5. Paradoxes of Induction / b. Raven paradox

19000	Read 'all ravens are black' as about ravens, not as about an implication [Belnap]
	Full Idea: 'All ravens are black' might profitably be read as saying not that being a raven 'implies' being black, but rather something more like 'Consider the ravens: each one is black'.
	From: Nuel D. Belnap (Conditional Assertion and Restricted Quantification [1970], p.7), quoted by Stephen Yablo - Aboutness 04.5
	A reaction: Belnap is more interested in the logic than in the paradox of confirmation, since he evidently thinks that universal generalisations should not be read as implications. I like Belnap's suggestion.

14. Science / D. Explanation / 2. Types of Explanation / a. Types of explanation

17897	Analytic explanation is wholes in terms of parts; synthetic is parts in terms of wholes or contexts [Belnap]
	Full Idea: Throughout the whole texture of philosophy we distinguish two modes of explanation: the analytic mode, which tends to explain wholes in terms of parts, and the synthetic mode, which explains parts in terms of the wholes or contexts in which they occur.
	From: Nuel D. Belnap (Tonk, Plonk and Plink [1962], p.132)
	A reaction: The analytic would be bottom-up, and the synthetic would be top-down. I'm inclined to combine them, and say explanation begins with a model, which can then be sliced in either direction, though the bottom looks more interesting.