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. |
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. |
3016 | Even the gods cannot strive against necessity [Pittacus, by Diog. Laertius] |
Full Idea: Even the gods cannot strive against necessity. | |
From: report of Pittacus (reports [c.610 BCE]) by Diogenes Laertius - Lives of Eminent Philosophers 01.5.4 |
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. |
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. |
6000 | The goal is rationality in the selection of things according to nature [Diogenes of Babylon, by Blank] |
Full Idea: Diogenes of Babylon defined the goal to be rationality in the selection and rejection of the things according to nature. | |
From: report of Diogenes (Bab) (fragments/reports [c.180 BCE]) by D.L. Blank - Diogenes of Babylon | |
A reaction: This captures the central Stoic idea quite nicely. 'Live according to nature', but this always meant 'live according to reason', because that is (as Aristotle had taught) the essence of our nature. This only makes sense if reason and nature coincide. |
5999 | The good is what is perfect by nature [Diogenes of Babylon, by Blank] |
Full Idea: Diogenes of Babylon defined the good as what is perfect by nature. | |
From: report of Diogenes (Bab) (fragments/reports [c.180 BCE]) by D.L. Blank - Diogenes of Babylon | |
A reaction: This might come close to G.E. Moore's Ideal Utilitarianism, but its dependence on the rather uneasy of concept of 'perfection' makes it questionable. Personally I find it appealing. I wish we had Diogenes' explanation. |
6001 | Justice is a disposition to distribute according to desert [Diogenes of Babylon, by Blank] |
Full Idea: Diogenes of Babylon defined justice as the disposition which distributes to everyone what he deserves. | |
From: report of Diogenes (Bab) (fragments/reports [c.180 BCE]) by D.L. Blank - Diogenes of Babylon | |
A reaction: The questions that arise would be 'what does a new-born baby deserve?', and 'what do animals deserve?', and 'does the lowest and worst of criminals deserve anything at all?' |