Combining Philosophers

Ideas for Anaxarchus, Rudolph Carnap and Henri Poincar

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4 ideas

6. Mathematics / C. Sources of Mathematics / 6. Logicism / a. Early logicism
Questions about numbers are answered by analysis, and are analytic, and hence logically true [Carnap]
     Full Idea: For the internal question like 'is there a prime number greater than a hundred?' the answers are found by logical analysis based on the rules for the new expressions. The answers here are analytic, i.e., logically true.
     From: Rudolph Carnap (Empiricism, Semantics and Ontology [1950], 2)
Logical positivists incorporated geometry into logicism, saying axioms are just definitions [Carnap, by Shapiro]
     Full Idea: The logical positivists brought geometry into the fold of logicism. The axioms of, say, Euclidean geometry are simply definitions of primitive terms like 'point' and 'line'.
     From: report of Rudolph Carnap (Empiricism, Semantics and Ontology [1950]) by Stewart Shapiro - Thinking About Mathematics 5.3
     A reaction: If the concept of 'line' is actually created by its definition, then we need to know exactly what (say) 'shortest' means. If we are merely describing a line, then our definition can be 'impredicative', using other accepted concepts.
6. Mathematics / C. Sources of Mathematics / 10. Constructivism / a. Constructivism
Convention, yes! Arbitrary, no! [Poincaré, by Putnam]
     Full Idea: Poincaré once exclaimed, 'Convention, yes! Arbitrary, no!'.
     From: report of Henri Poincaré (talk [1901]) by Hilary Putnam - Models and Reality
     A reaction: An interesting view. It mustn't be assumed that conventions are not rooted in something. Maybe a sort of pragmatism is implied.
6. Mathematics / C. Sources of Mathematics / 10. Constructivism / d. Predicativism
Avoid non-predicative classifications and definitions [Poincaré]
     Full Idea: Never consider any objects but those capable of being defined in a finite number of word ...Avoid non-predicative classifications and definitions.
     From: Henri Poincaré (The Logic of Infinity [1909], p.63), quoted by Penelope Maddy - Naturalism in Mathematics II.4