Combining Texts

Ideas for 'Defending the Axioms', 'Reason, Truth and History' and 'works'

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5 ideas

5. Theory of Logic / C. Ontology of Logic / 3. If-Thenism
Critics of if-thenism say that not all starting points, even consistent ones, are worth studying [Maddy]
     Full Idea: If-thenism denies that mathematics is in the business of discovering truths about abstracta. ...[their opponents] obviously don't regard any starting point, even a consistent one, as equally worthy of investigation.
     From: Penelope Maddy (Defending the Axioms [2011], 3.3)
     A reaction: I have some sympathy with if-thenism, in that you can obviously study the implications of any 'if' you like, but deep down I agree with the critics.
5. Theory of Logic / I. Semantics of Logic / 6. Intensionalism
Intension is not meaning, as 'cube' and 'square-faced polyhedron' are intensionally the same [Putnam]
     Full Idea: Intension cannot be identified with meaning. ..'Cube' and 'regular polyhedron with six square faces' are logically equivalent predicates. The intension is the same (the function giving the cubes in any possible world) but there is a difference of meaning.
     From: Hilary Putnam (Reason, Truth and History [1981], Ch.2)
5. Theory of Logic / J. Model Theory in Logic / 2. Isomorphisms
If cats equal cherries, model theory allows reinterpretation of the whole language preserving truth [Putnam]
     Full Idea: If the number of cats happens to equal the cherries, then it follows from the theory of models that there is a reinterpretation of the entire language that leaves all sentences unchanged in truth value while permuting the extensions of 'cat' and 'cherry'.
     From: Hilary Putnam (Reason, Truth and History [1981], Ch.2)
     A reaction: This horrifying result seems to come simply from the fact that there is an isomorphism between two models, which in turn seems to rest largely on the cardinality of the models. There seems to be something wrong with model theory here (?).
5. Theory of Logic / K. Features of Logics / 1. Axiomatisation
Hilbert's geometry and Dedekind's real numbers were role models for axiomatization [Maddy]
     Full Idea: At the end of the nineteenth century there was a renewed emphasis on rigor, the central tool of which was axiomatization, along the lines of Hilbert's axioms for geometry and Dedekind's axioms for real numbers.
     From: Penelope Maddy (Defending the Axioms [2011], 1.3)
If two mathematical themes coincide, that suggest a single deep truth [Maddy]
     Full Idea: The fact that two apparently fruitful mathematical themes turn out to coincide makes it all the more likely that they're tracking a genuine strain of mathematical depth.
     From: Penelope Maddy (Defending the Axioms [2011], 5.3ii)