5 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 |
| 19525 | If the only aim is to believe truths, that justifies recklessly believing what is unsupported (if it is right) [Conee/Feldman] |
| Full Idea: If it is intellectually required that one try to believe all and only truths (as Chisholm says), ...then it is possible to believe some unsubstantiated proposition in a reckless endeavour to believe a truth, and happen to be right. | |
| From: E Conee / R Feldman (Evidentialism [1985], 'Justification') | |
| A reaction: This implies doxastic voluntarism. Sorry! I meant, this implies that we can control what we believe, when actually we believe what impinges on us as facts. |
| 2614 | Modern phenomenalism holds that objects are logical constructions out of sense-data [Ayer] |
| Full Idea: Nowadays phenomenalism is held to be a theory of perception which says that physical objects are logical constructions out of sense-data. | |
| From: A.J. Ayer (Phenomenalism [1947], §1) |
| 2615 | The concept of sense-data allows us to discuss appearances without worrying about reality [Ayer] |
| Full Idea: The introduction of the term 'sense-datum' is a means of referring to appearances without prejudging the question of what it is, if anything, that they are appearances of. | |
| From: A.J. Ayer (Phenomenalism [1947], §1) |
| 19524 | We don't have the capacity to know all the logical consequences of our beliefs [Conee/Feldman] |
| Full Idea: Our limited cognitive capacities lead Goldman to deny a principle instructing people to believe all the logical consequences of their beliefs, since they are unable to have the infinite number of beliefs that following such a principle would require. | |
| From: E Conee / R Feldman (Evidentialism [1985], 'Doxastic') | |
| A reaction: This doesn't sound like much of an objection to epistemic closure, which I took to be the claim that you know the 'known' entailments of your knowledge. |