Combining Philosophers

Ideas for Archimedes, George Boolos and Scott Soames

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9 ideas

4. Formal Logic / D. Modal Logic ML / 1. Modal Logic
The interest of quantified modal logic is its metaphysical necessity and essentialism [Soames]
     Full Idea: The chief philosophical interest in quantified modal logic lies with metaphysical necessity, essentialism, and the nontrivial modal de re.
     From: Scott Soames (Philosophy of Language [2010], 3.1)
4. Formal Logic / F. Set Theory ST / 1. Set Theory
The logic of ZF is classical first-order predicate logic with identity [Boolos]
     Full Idea: The logic of ZF Set Theory is classical first-order predicate logic with identity.
     From: George Boolos (Must We Believe in Set Theory? [1997], p.121)
     A reaction: This logic seems to be unable to deal with very large cardinals, precisely those that are implied by set theory, so there is some sort of major problem hovering here. Boolos is fairly neutral.
4. Formal Logic / F. Set Theory ST / 4. Axioms for Sets / a. Axioms for sets
A few axioms of set theory 'force themselves on us', but most of them don't [Boolos]
     Full Idea: Maybe the axioms of extensionality and the pair set axiom 'force themselves on us' (Gödel's phrase), but I am not convinced about the axioms of infinity, union, power or replacement.
     From: George Boolos (Must We Believe in Set Theory? [1997], p.130)
     A reaction: Boolos is perfectly happy with basic set theory, but rather dubious when very large cardinals come into the picture.
4. Formal Logic / F. Set Theory ST / 4. Axioms for Sets / h. Axiom of Replacement VII
Do the Replacement Axioms exceed the iterative conception of sets? [Boolos, by Maddy]
     Full Idea: For Boolos, the Replacement Axioms go beyond the iterative conception.
     From: report of George Boolos (The iterative conception of Set [1971]) by Penelope Maddy - Naturalism in Mathematics I.3
4. Formal Logic / F. Set Theory ST / 5. Conceptions of Set / a. Sets as existing
The use of plurals doesn't commit us to sets; there do not exist individuals and collections [Boolos]
     Full Idea: We should abandon the idea that the use of plural forms commits us to the existence of sets/classes… Entities are not to be multiplied beyond necessity. There are not two sorts of things in the world, individuals and collections.
     From: George Boolos (To be is to be the value of a variable.. [1984]), quoted by Henry Laycock - Object
     A reaction: The problem of quantifying over sets is notoriously difficult. Try http://plato.stanford.edu/entries/object/index.html.
4. Formal Logic / F. Set Theory ST / 5. Conceptions of Set / d. Naïve logical sets
Naïve sets are inconsistent: there is no set for things that do not belong to themselves [Boolos]
     Full Idea: The naïve view of set theory (that any zero or more things form a set) is natural, but inconsistent: the things that do not belong to themselves are some things that do not form a set.
     From: George Boolos (Must We Believe in Set Theory? [1997], p.127)
     A reaction: As clear a summary of Russell's Paradox as you could ever hope for.
4. Formal Logic / F. Set Theory ST / 5. Conceptions of Set / e. Iterative sets
The iterative conception says sets are formed at stages; some are 'earlier', and must be formed first [Boolos]
     Full Idea: According to the iterative conception, every set is formed at some stage. There is a relation among stages, 'earlier than', which is transitive. A set is formed at a stage if and only if its members are all formed before that stage.
     From: George Boolos (Must We Believe in Set Theory? [1997], p.126)
     A reaction: He gives examples of the early stages, and says the conception is supposed to 'justify' Zermelo set theory. It is also supposed to make the axioms 'natural', rather than just being selected for convenience. And it is consistent.
4. Formal Logic / F. Set Theory ST / 5. Conceptions of Set / f. Limitation of Size
Limitation of Size is weak (Fs only collect is something the same size does) or strong (fewer Fs than objects) [Boolos, by Potter]
     Full Idea: Weak Limitation of Size: If there are no more Fs than Gs and the Gs form a collection, then Fs form a collection. Strong Limitation of Size: A property F fails to be collectivising iff there are as many Fs as there are objects.
     From: report of George Boolos (Iteration Again [1989]) by Michael Potter - Set Theory and Its Philosophy 13.5
4. Formal Logic / F. Set Theory ST / 8. Critique of Set Theory
Does a bowl of Cheerios contain all its sets and subsets? [Boolos]
     Full Idea: Is there, in addition to the 200 Cheerios in a bowl, also a set of them all? And what about the vast number of subsets of Cheerios? It is haywire to think that when you have some Cheerios you are eating a set. What you are doing is: eating the Cheerios.
     From: George Boolos (To be is to be the value of a variable.. [1984], p.72)
     A reaction: In my case Boolos is preaching to the converted. I am particularly bewildered by someone (i.e. Quine) who believes that innumerable sets exist while 'having a taste for desert landscapes' in their ontology.