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Ideas of Řystein Linnebo, by Text

[Norwegian, fl. 2006, Lecturer at Bristol University, then Birkbeck, London.]

2003 Plural Quantification Exposed
§0 p.71 Can second-order logic be ontologically first-order, with all the benefits of second-order?
     Full Idea: According to its supporters, second-order logic allow us to pay the ontological price of a mere first-order theory and get the corresponding monadic second-order theory for free.
     From: Řystein Linnebo (Plural Quantification Exposed [2003], §0)
§1 p.73 A comprehension axiom is 'predicative' if the formula has no bound second-order variables
     Full Idea: If φ contains no bound second-order variables, the corresponding comprehension axiom is said to be 'predicative'; otherwise it is 'impredicative'.
     From: Řystein Linnebo (Plural Quantification Exposed [2003], §1)
     A reaction: ['Predicative' roughly means that a new predicate is created, and 'impredicative' means that it just uses existing predicates]
§1 p.75 A 'pure logic' must be ontologically innocent, universal, and without presuppositions
     Full Idea: I offer these three claims as a partial analysis of 'pure logic': ontological innocence (no new entities are introduced), universal applicability (to any realm of discourse), and cognitive primacy (no extra-logical ideas are presupposed).
     From: Řystein Linnebo (Plural Quantification Exposed [2003], §1)
§2 p.78 The modern concept of an object is rooted in quantificational logic
     Full Idea: Our modern general concept of an object is given content only in connection with modern quantificational logic.
     From: Řystein Linnebo (Plural Quantification Exposed [2003], §2)
     A reaction: [He mentions Frege, Carnap, Quine and Dummett] This is the first thing to tell beginners in modern analytical metaphysics. The word 'object' is very confusing. I think I prefer 'entity'.
§4 p.88 Plural quantification depends too heavily on combinatorial and set-theoretic considerations
     Full Idea: If my arguments are correct, the theory of plural quantification has no right to the title 'logic'. ...The impredicative plural comprehension axioms depend too heavily on combinatorial and set-theoretic considerations.
     From: Řystein Linnebo (Plural Quantification Exposed [2003], §4)
2008 Plural Quantification
1 p.2 'Some critics admire only one another' cannot be paraphrased in singular first-order
     Full Idea: The Geach-Kaplan sentence 'Some critics admire only one another' provably has no singular first-order paraphrase using only its predicates.
     From: Řystein Linnebo (Plural Quantification [2008], 1)
     A reaction: There seems to be a choice of either going second-order (picking out a property), or going plural (collectively quantifying), or maybe both.
1.1 p.4 Predicates are 'distributive' or 'non-distributive'; do individuals do what the group does?
     Full Idea: The predicate 'is on the table' is 'distributive', since some things are on the table if each one is, whereas the predicate 'form a circle' is 'non-distributive', since it is not analytic that when some things form a circle, each one forms a circle.
     From: Řystein Linnebo (Plural Quantification [2008], 1.1)
     A reaction: The first predicate can have singular or plural subjects, but the second requires a plural subject? Hm. 'The rope forms a circle'. The second is example is not true, as well as not analytic.
2 p.5 Second-order quantification and plural quantification are different
     Full Idea: Second-order quantification and plural quantification are generally regarded as different forms of quantification.
     From: Řystein Linnebo (Plural Quantification [2008], 2)
2.4 p.8 Plural plurals are unnatural and need a first-level ontology
     Full Idea: Higher-order plural quantification (plural plurals) is often rejected because plural quantification is supposedly ontological innocent, with no plural things to be plural, and because it is not found in ordinary English.
     From: Řystein Linnebo (Plural Quantification [2008], 2.4)
     A reaction: [Summary; he cites Boolos as a notable rejector] Linnebo observes that Icelandic contains a word 'tvennir' which means 'two pairs of'.
2.4 p.9 Ordinary speakers posit objects without concern for ontology
     Full Idea: Maybe ordinary speakers aren't very concerned about their ontological commitments, and sometimes find it convenient to posit objects.
     From: Řystein Linnebo (Plural Quantification [2008], 2.4)
     A reaction: I think this is the whole truth about the ontological commitment of ordinary language. We bring abstraction under control by pretending it is a world of physical objects. The 'left wing' in politics, 'dark deeds', a 'huge difference'.
3 p.10 A pure logic is wholly general, purely formal, and directly known
     Full Idea: The defining features of a pure logic are its absolute generality (the objects of discourse are irrelevant), and its formality (logical truths depend on form, not matter), and its cognitive primacy (no extra-logical understanding is needed to grasp it).
     From: Řystein Linnebo (Plural Quantification [2008], 3)
     A reaction: [compressed] This strikes me as very important. The above description seems to contain no ontological commitment at all, either to the existence of something, or to two things, or to numbers, or to a property. Pure logic seems to be 'if-thenism'.
4.4 p.14 Plural quantification may allow a monadic second-order theory with first-order ontology
     Full Idea: Plural quantification seems to offer ontological economy. We can pay the price of a mere first-order theory and then use plural quantification to get for free the corresponding monadic second-order theory, which would be an ontological bargain.
     From: Řystein Linnebo (Plural Quantification [2008], 4.4)
     A reaction: [He mentions Hellman's modal structuralism in mathematics]
4.5 p.4 Instead of complex objects like tables, plurally quantify over mereological atoms tablewise
     Full Idea: Plural quantification can be used to eliminate the commitment of science and common sense to complex objects. We can use plural quantification over mereological atoms arranged tablewise or chairwise.
     From: Řystein Linnebo (Plural Quantification [2008], 4.5)
     A reaction: [He cites Hossack and van Ingwagen]
5 p.15 Traditionally we eliminate plurals by quantifying over sets
     Full Idea: The traditional view in analytic philosophy has been that all plural locutions should be paraphrased away by quantifying over sets, though Boolos and other objected that this is unnatural and unnecessary.
     From: Řystein Linnebo (Plural Quantification [2008], 5)
5.4 p.20 We speak of a theory's 'ideological commitments' as well as its 'ontological commitments'
     Full Idea: Some philosophers speak about a theory's 'ideological commitments' and not just about its 'ontological commitments'.
     From: Řystein Linnebo (Plural Quantification [2008], 5.4)
     A reaction: This is a third strategy for possibly evading one's ontological duty, along with fiddling with the words 'exist' or 'object'. An ideological commitment to something to which one is not actually ontologically committed conjures up stupidity and dogma.
2008 Structuralism and the Notion of Dependence
Intro p.59 Structuralism is right about algebra, but wrong about sets
     Full Idea: Against extreme views that all mathematical objects depend on the structures to which they belong, or that none do, I defend a compromise view, that structuralists are right about algebraic objects (roughly), but anti-structuralists are right about sets.
     From: Řystein Linnebo (Structuralism and the Notion of Dependence [2008], Intro)
1 p.60 'Deductivist' structuralism is just theories, with no commitment to objects, or modality
     Full Idea: The 'deductivist' version of eliminativist structuralism avoids ontological commitments to mathematical objects, and to modal vocabulary. Mathematics is formulations of various (mostly categorical) theories to describe kinds of concrete structures.
     From: Řystein Linnebo (Structuralism and the Notion of Dependence [2008], 1)
     A reaction: 'Concrete' is ambiguous here, as mathematicians use it for the actual working maths, as opposed to the metamathematics. Presumably the structures are postulated rather than described. He cites Russell 1903 and Putnam. It is nominalist.
I p.60 Non-eliminative structuralism treats mathematical objects as positions in real abstract structures
     Full Idea: The 'non-eliminative' version of mathematical structuralism takes it to be a fundamental insight that mathematical objects are really just positions in abstract mathematical structures.
     From: Řystein Linnebo (Structuralism and the Notion of Dependence [2008], I)
     A reaction: The point here is that it is non-eliminativist because it is committed to the existence of mathematical structures. I oppose this view, since once you are committed to the structures, you may as well admit a vast implausible menagerie of abstracta.
I p.60 'Modal' structuralism studies all possible concrete models for various mathematical theories
     Full Idea: The 'modal' version of eliminativist structuralism lifts the deductivist ban on modal notions. It studies what necessarily holds in all concrete models which are possible for various theories.
     From: Řystein Linnebo (Structuralism and the Notion of Dependence [2008], I)
     A reaction: [He cites Putnam 1967, and Hellman 1989] If mathematical truths are held to be necessary (which seems to be right), then it seems reasonable to include modal notions, about what is possible, in its study.
I p.61 'Set-theoretic' structuralism treats mathematics as various structures realised among the sets
     Full Idea: 'Set-theoretic' structuralism rejects deductive nominalism in favour of a background theory of sets, and mathematics as the various structures realized among the sets. This is often what mathematicians have in mind when they talk about structuralism.
     From: Řystein Linnebo (Structuralism and the Notion of Dependence [2008], I)
     A reaction: This is the big shift from 'mathematics can largely be described in set theory' to 'mathematics just is set theory'. If it just is set theory, then which version of set theory? Which axioms? The safe iterative conception, or something bolder?
II p.65 An 'intrinsic' property is either found in every duplicate, or exists independent of all externals
     Full Idea: There are two main ways of spelling out an 'intrinsic' property: if and only if it is shared by every duplicate of an object, ...and if and only if the object would have this property even if the rest of the universe were removed or disregarded.
     From: Řystein Linnebo (Structuralism and the Notion of Dependence [2008], II)
     A reaction: [He cites B.Weatherson's Stanford Encyclopaedia article] How about an intrinsic property being one which explains its identity, or behaviour, or persistence conditions?
III p.66 Structuralism differs from traditional Platonism, because the objects depend ontologically on their structure
     Full Idea: Structuralism can be distinguished from traditional Platonism in that it denies that mathematical objects from the same structure are ontologically independent of one another
     From: Řystein Linnebo (Structuralism and the Notion of Dependence [2008], III)
     A reaction: My instincts strongly cry out against all versions of this. If you are going to be a platonist (rather as if you are going to be religious) you might as well go for it big time and have independent objects, which will then dictate a structure.
III p.68 In mathematical structuralism the small depends on the large, which is the opposite of physical structures
     Full Idea: If objects depend on the other objects, this would mean an 'upward' dependence, in that they depend on the structure to which they belong, where the physical realm has a 'downward' dependence, with structures depending on their constituents.
     From: Řystein Linnebo (Structuralism and the Notion of Dependence [2008], III)
     A reaction: This nicely captures an intuition I have that there is something wrong with a commitment primarily to 'structures'. Our only conception of such things is as built up out of components. Not that I am committing to mathematical 'components'!
V p.73 There may be a one-way direction of dependence among sets, and among natural numbers
     Full Idea: We can give an exhaustive account of the identity of the empty set and its singleton without mentioning infinite sets, and it might be possible to defend the view that one natural number depends on its predecessor but not vice versa.
     From: Řystein Linnebo (Structuralism and the Notion of Dependence [2008], V)
     A reaction: Linnebo uses this as one argument against mathematical structuralism, where the small seems to depend on the large. The view of sets rests on the iterative conception, where each level is derived from a lower level. He dismisses structuralism of sets.