3 ideas
| 18758 | Validity is provable, but invalidity isn't, because the model is infinite [Church, by McGee] |
| Full Idea: Church showed that logic has a proof procedure, but no decision procedure. If an argument is invalid, there is a model with true premises and false conclusion, but the model will typically be infinite, so there is no way to display it concretely. | |
| From: report of Alonzo Church (A Note on the entscheidungsproblem [1936]) by Vann McGee - Logical Consequence 5 |
| 14528 | Maybe modal thought is unavoidable, as a priori recognition of necessary truth-preservation in reasoning [Hale/Hoffmann,A] |
| Full Idea: There are 'transcendental' arguments saying that modal thought is unavoidable - recognition, a priori, of the necessarily truth-preserving character of some forms of inference is a precondition for rational thought in general, and scientific theorizing. | |
| From: Bob Hale/ Aviv Hoffmann (Introduction to 'Modality' [2010], 1) | |
| A reaction: So the debate about the status of logical truths and valid inference, are partly debates about whether out thought has to involve modality, or whether it could just be about the actual world. I take possibilities and necssities to be features of nature. |
| 7295 | Maybe induction is only reliable IF reality is stable [Mitchell,A] |
| Full Idea: Maybe we should say that IF regularities are stable, only then is induction a reliable procedure. | |
| From: Alistair Mitchell (talk [2006]), quoted by PG - Db (ideas) | |
| A reaction: This seems to me a very good proposal. In a wildly unpredictable reality, it is hard to see how anyone could learn from experience, or do any reasoning about the future. Natural stability is the axiom on which induction is built. |