12 ideas
| 16985 | Possible worlds allowed the application of set-theoretic models to modal logic [Kripke] |
| Full Idea: The main and the original motivation for the 'possible worlds analysis' - and the way it clarified modal logic - was that it enabled modal logic to be treated by the same set theoretic techniques of model theory used successfully in extensional logic. | |
| From: Saul A. Kripke (Naming and Necessity preface [1980], p.19 n18) | |
| A reaction: So they should be ascribed the same value that we attribute to classical model theory, whatever that is. |
| 15102 | S4 says there must be some necessary truths (the actual ones, of which there is at least one) [Cameron] |
| Full Idea: S4 says there must be some necessary truths, because the actual necessary truths must be necessary. (It says if there are some actual necessary truths then that is so - but the S4 axiom is an actual necessary truth, if true). | |
| From: Ross P. Cameron (On the Source of Necessity [2010], 2) |
| 16982 | A man has two names if the historical chains are different - even if they are the same! [Kripke] |
| Full Idea: Two totally distinct 'historical chains' that be sheer accident assign the same name to the same man should probably count as creating distinct names despite the identity of the referents. | |
| From: Saul A. Kripke (Naming and Necessity preface [1980], p.08 n9) | |
| A reaction: A nice puzzle for his own theory. 'What's you name?' 'Alice, and Alice!' |
| 16981 | With the necessity of self-identity plus Leibniz's Law, identity has to be an 'internal' relation [Kripke] |
| Full Idea: It is clear from (x)□(x=x) and Leibniz's Law that identity is an 'internal' relation: (x)(y)(x=y ⊃ □x=y). What pairs (w,y) could be counterexamples? Not pairs of distinct objects, …nor an object and itself. | |
| From: Saul A. Kripke (Naming and Necessity preface [1980], p.03) | |
| A reaction: I take 'internal' to mean that the necessity of identity is intrinsic to the item(s), and not imposed by some other force. |
| 4942 | The indiscernibility of identicals is as self-evident as the law of contradiction [Kripke] |
| Full Idea: It seems to me that the Leibnizian principle of the indiscernibility of identicals (not to be confused with the identity of indiscernibles) is as self-evident as the law of contradiction. | |
| From: Saul A. Kripke (Naming and Necessity preface [1980], p.03) | |
| A reaction: This seems obviously correct, as it says no more than that a thing has whatever properties it has. If a difference is discerned, either you have made a mistake, or it isn't identical. |
| 16984 | I don't think possible worlds reductively reveal the natures of modal operators etc. [Kripke] |
| Full Idea: I do not think of 'possible worlds' as providing a reductive analysis in any philosophically significant sense, that is, as uncovering the ultimate nature, from either an epistemological or a metaphysical view, of modal operators, propositions etc. | |
| From: Saul A. Kripke (Naming and Necessity preface [1980], p.19 n18) | |
| A reaction: I think this remark opens the door for Kit Fine's approach, of showing what modality is by specifying its sources. Possible worlds model the behaviour of modal inferences. |
| 15103 | Blackburn fails to show that the necessary cannot be grounded in the contingent [Cameron] |
| Full Idea: I conclude that Blackburn has not shown that any grounding of the necessary in the contingent (the Contingency Horn of his dilemma) is doomed to failure. | |
| From: Ross P. Cameron (On the Source of Necessity [2010], 2) | |
| A reaction: [You must read the article for details of Cameron's argument!] He goes on to also reject the Necessity Horn (that there is a regress if necessities must rely on necessities). |
| 9385 | The very act of designating of an object with properties gives knowledge of a contingent truth [Kripke] |
| Full Idea: If a speaker introduced a designator into a language by a ceremony, then in virtue of his very linguistic act, he would be in a position to say 'I know that Fa', but nevertheless 'Fa' would be a contingent truth (provided F is not an essential property). | |
| From: Saul A. Kripke (Naming and Necessity preface [1980], p.14) | |
| A reaction: If someone else does the designation, I seem to have contingent knowledge that the ceremony has taken place. You needn't experience the object, but you must experience the ceremony, even if you perform it. |
| 4943 | Instead of talking about possible worlds, we can always say "It is possible that.." [Kripke] |
| Full Idea: We should remind ourselves the 'possible worlds' terminology can always be replaced by modal talk, such as "It is possible that…" | |
| From: Saul A. Kripke (Naming and Necessity preface [1980], p.15) | |
| A reaction: Coming from an originator of the possible worlds idea, this is a useful reminder that we don't have to get too excited about the ontological commitments involved. It may be just a 'way to talk', and hence a tool, rather than a truth about reality. |
| 16983 | Probability with dice uses possible worlds, abstractions which fictionally simplify things [Kripke] |
| Full Idea: In studying probabilities with dice, we are introduced at a tender age to a set of 36 (miniature) possible worlds, if we (fictively) ignore everything except the two dice. …The possibilities are abstract states of the dice, not physical entities. | |
| From: Saul A. Kripke (Naming and Necessity preface [1980], p.16) | |
| A reaction: Interesting for the introduction by the great man of the words 'fictional' and 'abstract' into the discussion. He says elsewhere that he takes worlds to be less than real, but more than mere technical devices. |
| 15877 | The aim of science is just to create a comprehensive, elegant language to describe brute facts [Poincaré, by Harré] |
| Full Idea: In Poincaré's view, we try to construct a language within which the brute facts of experience are expressed as comprehensively and as elegantly as possible. The job of science is the forging of a language precisely suited to that purpose. | |
| From: report of Henri Poincaré (The Value of Science [1906], Pt III) by Rom Harré - Laws of Nature 2 | |
| A reaction: I'm often struck by how obscure and difficult our accounts of self-evident facts can be. Chairs are easy, and the metaphysics of chairs is hideous. Why is that? I'm a robust realist, but I like Poincaré's idea. He permits facts. |
| 15104 | The 'moving spotlight' theory makes one time privileged, while all times are on a par ontologically [Cameron] |
| Full Idea: What seems so wrong about the 'moving spotlight' theory is that here one time is privileged, but all the times are on a par ontologically. | |
| From: Ross P. Cameron (On the Source of Necessity [2010], 4) | |
| A reaction: The whole thing is baffling, but this looks like a good point. All our intuitions make presentism (there's only the present) look like a better theory than the moving spotlight (that the present is just 'special'). |