16 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. |
9406 | A class is natural when everybody can spot further members of it [Quinton] |
Full Idea: To say that a class is natural is to say that when some of its members are shown to people they pick out others without hesitation and in agreement. | |
From: Anthony Quinton (The Nature of Things [1973], 9 'Nat') | |
A reaction: He concedes a number of problems with his view, but I admire his attempt to at least begin to distinguish the natural (real!) classes from the ersatz ones. A mention of causal powers would greatly improve his story. |
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!' |
15730 | Extreme nominalists say all classification is arbitrary convention [Quinton] |
Full Idea: Pure, extreme nominalism sees all classification as the product of arbitrary convention. | |
From: Anthony Quinton (The Nature of Things [1973], 9 'Nat') | |
A reaction: I'm not sure what the word 'arbitrary' is doing there. Nominalists are not daft, and if they can classify any way they like, they are not likely to choose an 'arbitrary' system. Pragmatism tells the right story here. |
15728 | The naturalness of a class depends as much on the observers as on the objects [Quinton] |
Full Idea: The naturalness of a class depends as essentially on the nature of the observers who classify as it does on the nature of the objects that they classify. ...It depends on our perceptual apparatus, and on our relatively mutable needs and interests. | |
From: Anthony Quinton (The Nature of Things [1973], 9 'Nat') | |
A reaction: This seems to translate 'natural' as 'natural for us', which is not much use to scientists, who spend quite a lot of effort combating folk wisdom. Do desirable sports cars constitute a natural class? |
9407 | Properties imply natural classes which can be picked out by everybody [Quinton] |
Full Idea: To say there are properties is to say there are natural classes, classes introduction to some of whose members enables people to pick out others without hesitation and in agreement. | |
From: Anthony Quinton (The Nature of Things [1973], 9 'Nat') | |
A reaction: Aristotle would like this approach, but it doesn't find many friends among modern logician/philosophers. We should go on to ask why people agree on these things. Causal powers will then come into it. |
15729 | Uninstantiated properties must be defined using the instantiated ones [Quinton] |
Full Idea: Properties that have no concrete instances must be defined in terms of those that have. | |
From: Anthony Quinton (The Nature of Things [1973], 9 'Nat') | |
A reaction: I wonder what the dodo used to smell like? |
8520 | An individual is a union of a group of qualities and a position [Quinton, by Campbell,K] |
Full Idea: Quinton proposes that an individual is a union of a group of qualities and a position. | |
From: report of Anthony Quinton (The Nature of Things [1973], Pt I) by Keith Campbell - The Metaphysic of Abstract Particulars §5 | |
A reaction: This seems the obvious defence of a bundle account of objects against the charge that indiscernibles would have to be identical. It introduces, however, 'positions' into the ontology, but maybe that price must be paid. Materialism needs space. |
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. |
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. |
13304 | Learned men gain more in one day than others do in a lifetime [Posidonius] |
Full Idea: In a single day there lies open to men of learning more than there ever does to the unenlightened in the longest of lifetimes. | |
From: Posidonius (fragments/reports [c.95 BCE]), quoted by Seneca the Younger - Letters from a Stoic 078 | |
A reaction: These remarks endorsing the infinite superiority of the educated to the uneducated seem to have been popular in late antiquity. It tends to be the religions which discourage great learning, especially in their emphasis on a single book. |
20820 | Time is an interval of motion, or the measure of speed [Posidonius, by Stobaeus] |
Full Idea: Posidonius defined time thus: it is an interval of motion, or the measure of speed and slowness. | |
From: report of Posidonius (fragments/reports [c.95 BCE]) by John Stobaeus - Anthology 1.08.42 | |
A reaction: Hm. Can we define motion or speed without alluding to time? Looks like we have to define them as a conjoined pair, which means we cannot fully understand either of them. |