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Ideas for 'The Social Contract (tr Cress)', 'A Subject with No Object' and 'Philosophy of Mathematics'

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7 ideas

6. Mathematics / A. Nature of Mathematics / 3. Nature of Numbers / a. Numbers
We should talk about possible existence, rather than actual existence, of numbers [Burgess/Rosen]
     Full Idea: The modal strategy for numbers is to replace assumptions about the actual existence of numbers by assumptions about the possible existence of numbers
     From: JP Burgess / G Rosen (A Subject with No Object [1997], II.B.3.a)
     A reaction: This seems to be quite a good way of dealing with very large numbers and infinities. It is not clear whether 5 is so regularly actualised that we must consider it as permanent, or whether it is just a prominent permanent possibility.
6. Mathematics / B. Foundations for Mathematics / 4. Axioms for Number / g. Incompleteness of Arithmetic
You can't prove consistency using a weaker theory, but you can use a consistent theory [Linnebo]
     Full Idea: If the 2nd Incompleteness Theorem undermines Hilbert's attempt to use a weak theory to prove the consistency of a strong one, it is still possible to prove the consistency of one theory, assuming the consistency of another theory.
     From: Øystein Linnebo (Philosophy of Mathematics [2017], 4.6)
     A reaction: Note that this concerns consistency, not completeness.
6. Mathematics / B. Foundations for Mathematics / 7. Mathematical Structuralism / a. Structuralism
Mathematics is the study of all possible patterns, and is thus bound to describe the world [Linnebo]
     Full Idea: Philosophical structuralism holds that mathematics is the study of abstract structures, or 'patterns'. If mathematics is the study of all possible patterns, then it is inevitable that the world is described by mathematics.
     From: Øystein Linnebo (Philosophy of Mathematics [2017], 11.1)
     A reaction: [He cites the physicist John Barrow (2010) for this] For me this is a major idea, because the concept of a pattern gives a link between the natural physical world and the abstract world of mathematics. No platonism is needed.
6. Mathematics / B. Foundations for Mathematics / 7. Mathematical Structuralism / c. Nominalist structuralism
Structuralism and nominalism are normally rivals, but might work together [Burgess/Rosen]
     Full Idea: Usually structuralism and nominalism are considered rivals. But structuralism can also be the first step in a strategy of nominalist reconstrual or paraphrase.
     From: JP Burgess / G Rosen (A Subject with No Object [1997], II.C.0)
     A reaction: Hellman and later Chihara seem to be the main proponents of nominalist structuralism. My sympathies lie with this strategy. Are there objects at the nodes of the structure, or is the structure itself platonic? Mill offers a route.
6. Mathematics / C. Sources of Mathematics / 1. Mathematical Platonism / b. Against mathematical platonism
Number words became nouns around the time of Plato [Burgess/Rosen]
     Full Idea: The transition from using number words purely as adjectives to using them extensively as nouns has been traced to 'around the time of Plato'.
     From: JP Burgess / G Rosen (A Subject with No Object [1997], III.C.2.a)
     A reaction: [The cite Kneale and Kneale VI,§2 for this] It is just too tempting to think that in fact Plato (and early Platonists) were totally responsible for this shift, since the whole reification of numbers seems to be inherently platonist.
6. Mathematics / C. Sources of Mathematics / 6. Logicism / d. Logicism critique
Logical truth is true in all models, so mathematical objects can't be purely logical [Linnebo]
     Full Idea: Modern logic requires that logical truths be true in all models, including ones devoid of any mathematical objects. It follows immediately that the existence of mathematical objects can never be a matter of logic alone.
     From: Øystein Linnebo (Philosophy of Mathematics [2017], 2)
     A reaction: Hm. Could there not be a complete set of models for a theory which all included mathematical objects? (I can't answer that).
6. Mathematics / C. Sources of Mathematics / 7. Formalism
Game Formalism has no semantics, and Term Formalism reduces the semantics [Linnebo]
     Full Idea: Game Formalism seeks to banish all semantics from mathematics, and Term Formalism seeks to reduce any such notions to purely syntactic ones.
     From: Øystein Linnebo (Philosophy of Mathematics [2017], 3.3)
     A reaction: This approach was stimulated by the need to justify the existence of the imaginary number i. Just say it is a letter!