### Ideas from 'Logicism Revisited' by Alan Musgrave [1977], by Theme Structure

#### [found in 'British Soc for the Philosophy of Science' (ed/tr -) [- ,]].

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###### 5. Theory of Logic / C. Ontology of Logic / 3. If-Thenism
 10061 The If-thenist view only seems to work for the axiomatised portions of mathematics
 Full Idea: The If-thenist view seems to apply straightforwardly only to the axiomatised portions of mathematics. From: Alan Musgrave (Logicism Revisited [1977], §5) A reaction: He cites Lakatos to show that cutting-edge mathematics is never axiomatised. One might reply that if the new mathematics is any good then it ought to be axiomatis-able (barring Gödelian problems).
 10065 Perhaps If-thenism survives in mathematics if we stick to first-order logic
 Full Idea: If we identify logic with first-order logic, and mathematics with the collection of first-order theories, then maybe we can continue to maintain the If-thenist position. From: Alan Musgrave (Logicism Revisited [1977], §5) A reaction: The problem is that If-thenism must rely on rules of inference. That seems to mean that what is needed is Soundness, rather than Completeness. That is, inference by the rules must work properly.
###### 5. Theory of Logic / I. Semantics of Logic / 3. Logical Truth
 10049 Logical truths may contain non-logical notions, as in 'all men are men'
 Full Idea: Containing only logical notions is not a necessary condition for being a logical truth, since a logical truth such as 'all men are men' may contain non-logical notions such as 'men'. From: Alan Musgrave (Logicism Revisited [1977], §3) A reaction: [He attributes this point to Russell] Maybe it is only a logical truth in its general form, as ∀x(x=x). Of course not all 'banks' are banks.
 10050 A statement is logically true if it comes out true in all interpretations in all (non-empty) domains
 Full Idea: The standard modern view of logical truth is that a statement is logically true if it comes out true in all interpretations in all (non-empty) domains. From: Alan Musgrave (Logicism Revisited [1977], §3)
###### 6. Mathematics / B. Foundations for Mathematics / 4. Axioms for Number / d. Peano arithmetic
 10058 No two numbers having the same successor relies on the Axiom of Infinity
 Full Idea: The axiom of Peano which states that no two numbers have the same successor requires the Axiom of Infinity for its proof. From: Alan Musgrave (Logicism Revisited [1977], §4 n) A reaction: [He refers to Russell 1919:131-2] The Axiom of Infinity is controversial and non-logical.
###### 6. Mathematics / C. Sources of Mathematics / 7. Formalism
 10063 Formalism is a bulwark of logical positivism
 Full Idea: Formalism is a bulwark of logical positivist philosophy. From: Alan Musgrave (Logicism Revisited [1977], §5) A reaction: Presumably if you drain all the empirical content out of arithmetic and geometry, you are only left with the bare formal syntax, of symbols and rules. That seems to be as analytic as you can get.
 10062 Formalism seems to exclude all creative, growing mathematics
 Full Idea: Formalism seems to exclude from consideration all creative, growing mathematics. From: Alan Musgrave (Logicism Revisited [1977], §5) A reaction: [He cites Lakatos in support] I am not immediately clear why spotting the remote implications of a formal system should be uncreative. The greatest chess players are considered to be highly creative and imaginative.