16 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? |
| 6017 | Nomos is king [Pindar] |
| Full Idea: Nomos is king. | |
| From: Pindar (poems [c.478 BCE], S 169), quoted by Thomas Nagel - The Philosophical Culture | |
| A reaction: This seems to be the earliest recorded shot in the nomos-physis wars (the debate among sophists about moral relativism). It sounds as if it carries the full relativist burden - that all that matters is what has been locally decreed. |
| 21243 | An existing thing is even greater if its non-existence is inconceivable [Anselm] |
| Full Idea: Something can be thought of as existing, which cannot be thought of as not existing, and this is greater than that which cannot be thought of as not existing. | |
| From: Anselm (Proslogion [1090], Ch 3) | |
| A reaction: This is a necessary addition, to single out the concept of God as special. But you really must give reasons for saying God's non-existence is inconceivable. Atheists seem to manage. |
| 21244 | Conceiving a greater being than God leads to absurdity [Anselm] |
| Full Idea: If some mind could think of something better than thou, the creature would rise above the Creator and judge its Creator; but this is altogether absurd. | |
| From: Anselm (Proslogion [1090], Ch 3) | |
| A reaction: An error, revealing a certain desperation. If a greafer being could be conceived than the being so far imagined as God (a necessarily existing being), that being would BE God, by his own argument (and not some arrogant 'creature'). |
| 21241 | Even the fool can hold 'a being than which none greater exists' in his understanding [Anselm] |
| Full Idea: Even the fool must be convinced that a being than which none greater can be thought exists at least in his understanding, since when he hears this he understands it, and whatever is understood is in the understanding. | |
| From: Anselm (Proslogion [1090], Ch 2) | |
| A reaction: Psalm 14.1: 'The fool hath said in his heart, there is no God'. But how does the fool interpret the words, if he has limited imagination? He might get no further than an attractive film star. He would need prompting to think of a spiritual being. |
| 21242 | If that than which a greater cannot be thought actually exists, that is greater than the mere idea [Anselm] |
| Full Idea: Clearly that than which a greater cannot be thought cannot exist in the understanding alone. For it it is actually in the understanding alone, it can be thought of as existing also in reality, and this is greater. | |
| From: Anselm (Proslogion [1090], Ch 2) | |
| A reaction: The suppressed premise is 'something actually existing is greater than the mere conception of it'. As it stands this is wrong. I can imagine a supreme evil. But see Idea 21243. |
| 1421 | A perfection must be independent and unlimited, and the necessary existence of Anselm's second proof gives this [Malcolm on Anselm] |
| Full Idea: Anselm's second proof works, because he sees that necessary existence (or the impossibility of non-existence) really is a perfection. This is because a perfection requires no dependence or limit or impediment. | |
| From: comment on Anselm (Proslogion [1090], Ch 3) by Norman Malcolm - Anselm's Argument Sect II | |
| A reaction: I have the usual problem, that it doesn't seem to follow that the perfect existence of something bestows a perfection. It may be necessary that 'for every large animal there exists a disease'. Satan may exist necessarily. |
| 21245 | The word 'God' can be denied, but understanding shows God must exist [Anselm] |
| Full Idea: We think of a thing when we say the world, and in another way when we think of the very thing itself. In the second sense God cannot be thought of as nonexistent. No one who understands can think God does not exist. | |
| From: Anselm (Proslogion [1090], Ch 4) | |
| A reaction: It seems open to the atheist to claim the exact opposite - that you can commit to God's existence if it is just a word, but understanding shows that God is impossible (perhaps because of contradictions). How to arbitrate? |
| 21246 | Guanilo says a supremely fertile island must exist, just because we can conceive it [Anselm] |
| Full Idea: Guanilo supposes that we imagine an island surpassing all lands in its fertility. We might then say that we cannot doubt that it truly exists is reality, because anyone can conceive it from a verbal description. | |
| From: Anselm (Proslogion [1090], Reply 3) | |
| A reaction: Guanilo was a very naughty monk, who must have had sleepless nights over this. One could further ask whether an island might have necessary existence. Anselm needs 'a being' to be a special category of thing. |
| 21247 | Nonexistence is impossible for the greatest thinkable thing, which has no beginning or end [Anselm] |
| Full Idea: If anyone does think of something a greater than which cannot be thought, then he thinks of something which cannot be thought of as nonexistent, ...for then it could be thought of as having a beginning and an end. And this is impossible. | |
| From: Anselm (Proslogion [1090], Reply 3) | |
| A reaction: A nice idea, but it has a flip side. If the atheist denies God's existence, then it follows that (because no beginning is possible for such a being) the existence of God is impossible. Anselm adds that contingent existents have parts (unlike God). |
| 1420 | Anselm's first proof fails because existence isn't a real predicate, so it can't be a perfection [Malcolm on Anselm] |
| Full Idea: Anselm's first proof fails, because he treats existence as being a perfection, which it isn't, because that would make it a real predicate. | |
| From: comment on Anselm (Proslogion [1090], Ch 2) by Norman Malcolm - Anselm's Argument Sect I | |
| A reaction: Not everyone accepts Kant's claim that existence cannot be a predicate. They all seem to know what a perfection is. Can the Mona Lisa (an object) not be a perfection? Must it be broken down into perfect predicates? |