display all the ideas for this combination of texts
4 ideas
8941 | We can't explain 'possibility' in terms of 'possible' worlds [Fisher] |
Full Idea: Explaining 'it is possible that p' by saying p is true in at least one possible world doesn't get me very far. If I don't understand what possibility is, then appealing to possible worlds is not going to do me much good. | |
From: Jennifer Fisher (On the Philosophy of Logic [2008], 06.III) | |
A reaction: This seems so blatant that I assume friends of possible worlds will have addressed the problem. Note that you will also need to understand 'possible' to define necessity as 'true in all possible worlds'. Necessarily-p is not-possibly-not-p. |
21533 | Contingency arises from tensed verbs changing the propositions to which they refer [Russell] |
Full Idea: Contingency derives from the fact that a sentence containing a verb in the present tense - or sometimes in the past or the future - changes its meaning continually as the present changes, and stands for different propositions at different times. | |
From: Bertrand Russell (Meinong on Complexes and Assumptions [1904], p.26) | |
A reaction: This immediately strikes me as a bad example of the linguistic approach to philosophy. As if we (like any animal) didn't have an apprehension prior to any language that most parts of experience are capable of change. |
8947 | If all truths are implied by a falsehood, then not-p might imply both q and not-q [Fisher] |
Full Idea: If all truths are implied by a falsehood, then 'if there are no trees in the park then there is no shade' and 'if there are no trees in the park there is plenty of shade' both come out as true. Intuitively, though, the second one is false. | |
From: Jennifer Fisher (On the Philosophy of Logic [2008], 08.I) | |
A reaction: The rule that a falsehood implies all truths must be the weakest idea in classical logic, if it actually implies a contradiction. This means we must take an interest in relevance logics. |
8949 | In relevance logic, conditionals help information to flow from antecedent to consequent [Fisher] |
Full Idea: A good account of relevance logic suggests that a conditional will be true when the flow of information is such that a conditional is the device that helps information to flow from the antecedent to the consequent. | |
From: Jennifer Fisher (On the Philosophy of Logic [2008], 08.III) | |
A reaction: Hm. 'If you are going out, you'll need an umbrella'. This passes on information about 'out', but also brings in new information. 'If you are going out, I'm leaving you'. What flows is an interpretation of the antecedent. Tricky. |