13 ideas
| 10061 | The If-thenist view only seems to work for the axiomatised portions of mathematics [Musgrave] |
| 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 [Musgrave] |
| 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. |
| 10049 | Logical truths may contain non-logical notions, as in 'all men are men' [Musgrave] |
| 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 [Musgrave] |
| 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) |
| 10058 | No two numbers having the same successor relies on the Axiom of Infinity [Musgrave] |
| 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. |
| 10062 | Formalism seems to exclude all creative, growing mathematics [Musgrave] |
| 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. |
| 10063 | Formalism is a bulwark of logical positivism [Musgrave] |
| 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. |
| 22200 | If you eliminate the impossible, the truth will remain, even if it is weird [Conan Doyle] |
| Full Idea: When you have eliminated the impossible, whatever remains, however improbable, must be the truth. | |
| From: Arthur Conan Doyle (The Sign of Four [1890], Ch. 6) | |
| A reaction: A beautiful statement, by Sherlock Holmes, of Eliminative Induction. It is obviously not true, of course. Many options may still face you after you have eliminated what is actually impossible. |
| 10060 | Logical positivists adopted an If-thenist version of logicism about numbers [Musgrave] |
| Full Idea: Logical positivists did not adopt old-style logicism, but rather logicism spiced with varying doses of If-thenism. | |
| From: Alan Musgrave (Logicism Revisited [1977], §4) | |
| A reaction: This refers to their account of mathematics as a set of purely logical truths, rather than being either empirical, or a priori synthetic. |
| 23569 | The only just cause for a war is a wrong received [Vitoria] |
| Full Idea: There is a single and only just cause for commencing a war, namely, a wrong received. | |
| From: Francis de Vitoria (On the Law of War [1525], p.170), quoted by Michael Walzer - Just and Unjust Wars 04 | |
| A reaction: Walzer affirms this as one the principles of international law. In particular, mere differences of religion or politics cannot justify a war. The tricky bit is when the participants don't agree on the severity of the wrong. |
| 23601 | Leaders can only attack foreigners who have done wrong (as with their own subjects) [Vitoria] |
| Full Idea: A political leader cannot have greater authority over foreigners than over his own subjects; but he may not draw the sword against his own subjects unless they have done wrong; therefore he can only do so against foreigners in the same circumstances. | |
| From: Francis de Vitoria (On the Law of War [1525], p.303), quoted by Jeff McMahan - Killing in War 1.4 | |
| A reaction: The question would then be whether they have 'done some wrong' against this leader, or against some other people (such as their fellow citizens). That would be the 'intervention' justification. Are they engaged in the wrong, or responsible for it? |
| 23566 | Princes should not justify a war to their subjects, and doing so would undermine the state [Vitoria] |
| Full Idea: A prince is not able and ought not always to render reasons for the war to its subjects, and if the subjects cannot serve in the war except they be satisfied of its justice, the state would fall into grave peril. | |
| From: Francis de Vitoria (On the Law of War [1525], p.176), quoted by Michael Walzer - Just and Unjust Wars 03 | |
| A reaction: This medieval view depends entirely on the absolute sovereignty of princes, and confidence that princes are wise and innately just. No student of history should believe such wicked nonsense. |
| 23576 | Sacking a city is lawful if it motivates the attacking troops [Vitoria] |
| Full Idea: It is not unlawful to put a city to sack, if it is necessary for the conduct of the war …as a spur to the courage of the troops. | |
| From: Francis de Vitoria (On the Law of War [1525], p.184), quoted by Michael Walzer - Just and Unjust Wars 08 | |
| A reaction: Hideous. Presumably this would include raping the women. Could you motivate a football team in a similar way? Or to get your children to pass exams? |