10 ideas
9456 | Modal logic is multiple systems, shown in the variety of accessibility relations between worlds [Jacquette] |
Full Idea: Modal logic by its very nature is not monolithic, but fragmented into multiple systems of modal qualifications, reflected in the plurality of accessibility relations on modal model structures or logically possible worlds. | |
From: Dale Jacquette (Intro to 'Philosophy of Logic' [2002], §3) | |
A reaction: He implies the multiplicity is basic, and is only 'reflected' in the relations, but maybe the multiplicity is caused by incompetent logicians who can't decide whether possible worlds really are reflexive or symmetrical or transitive in their relations. |
9457 | The two main views in philosophy of logic are extensionalism and intensionalism [Jacquette] |
Full Idea: Philosophy of logic has (roughly) two camps: extensionalists and intensionalists, with the former view dominant. ...There is a close connection between this and eliminativist or reductivist versus folk psychological and intentionalist philosophy of mind. | |
From: Dale Jacquette (Intro to 'Philosophy of Logic' [2002], §4) | |
A reaction: Hm. I think I favour intensionalism in the logic, and reductivism about the mind, so I may have a bit of bother here. I'm convinced that this jigsaw can be completed, despite all appearances. |
9458 | Extensionalists say that quantifiers presuppose the existence of their objects [Jacquette] |
Full Idea: Extensionalists hold that quantifiers in predicate logic presuppose the existence of whatever objects can be referred to by constants or bound variables, or enter into true predication of properties. | |
From: Dale Jacquette (Intro to 'Philosophy of Logic' [2002], §4) | |
A reaction: I have strong sales resistance to this view. Why should a procedure for correctly reasoning from one proposition to another have anything whatever to do with ontology? A false world picture can be interconnected by perfect logic. |
9461 | Intensionalists say meaning is determined by the possession of properties [Jacquette] |
Full Idea: According to intensionalist semantics the meaning of a proposition is determined by the properties an object possesses. | |
From: Dale Jacquette (Intro to 'Philosophy of Logic' [2002], §4) | |
A reaction: This sounds good to me. Extensionalist don't seem to care what sets they put things in, but if property possession comes first, then things will fall into their own sets without any help for us. We can add silly sets afterwards, if we fancy. |
9460 | Extensionalist semantics forbids reference to nonexistent objects [Jacquette] |
Full Idea: In extensionalist semantics only existent objects can be referred to, ...but in everyday thought and discourse we regularly and apparently without undue confusion speak about nonexistent objects. | |
From: Dale Jacquette (Intro to 'Philosophy of Logic' [2002], §4) | |
A reaction: This is the reason why Meinong, whose views are presented by Russell as absurd, are undergoing a revival. The full-blown view will even treat 'round squares' as objects about which we can reason - and why not? Don't open a shop which sells them. |
9459 | Extensionalist semantics is circular, as we must know the extension before assessing 'Fa' [Jacquette] |
Full Idea: Extensional semantics is blatantly circular. For 'Fa' to be interpreted as true, we must know that object a belongs to the extension of the predicate F, so we must already know which objects belong to the extension. | |
From: Dale Jacquette (Intro to 'Philosophy of Logic' [2002], §4) | |
A reaction: I'm delighted to read this, because it was the first thought that occurred to me when I encountered the theory. Presumably this leads Quine to take predication as basic, because you can't break into the circle. Or, vote for intensionalism? |
468 | Musical performance can reveal a range of virtues [Damon of Ath.] |
Full Idea: In singing and playing the lyre, a boy will be likely to reveal not only courage and moderation, but also justice. | |
From: Damon (fragments/reports [c.460 BCE], B4), quoted by (who?) - where? |
22485 | Non-cognitivists give the conditions of use of moral sentences as facts about the speaker [Foot] |
Full Idea: What all these [non-cognitivist] theories try to do is to give the conditions of use of sentences such as 'It is morally objectionable to break promises', in terms of something which must be true about the speaker. | |
From: Philippa Foot (Does Moral Subjectivism Rest on a Mistake? [1995], p.192) | |
A reaction: A wonderfully simple and accurate analysis of this view. Compare analysing 'there is a bus coming towards you' in the same way. Sounds silly, but lots of modern philosophers see things that way. |
22486 | The mistake is to think good grounds aren't enough for moral judgement, which also needs feelings [Foot] |
Full Idea: The mistake is to think that whatever 'grounds' for a moral judgement may have been given, someone may be unready, indeed unable, to make the moral judgement, because he has not got the attitude or feeling. | |
From: Philippa Foot (Does Moral Subjectivism Rest on a Mistake? [1995], p.192) | |
A reaction: This is roughly the Frege-Geach problem for expressivism, of how we still make moral judgements about situations where we ourselves are entirely disinterested (such as ancient historical events). |
22487 | Moral arguments are grounded in human facts [Foot] |
Full Idea: The grounding of a moral argument is ultimately in facts about human life. | |
From: Philippa Foot (Does Moral Subjectivism Rest on a Mistake? [1995], p.207) | |
A reaction: The best slogan I can find for summarising Foot's metaethics. The facts she refers to the basic human needs. She is right, and this almost bridges the fact-value divide (as long as you give a damn about human needs). |