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All the ideas for 'Actualism and Possible Worlds', 'works' and 'Philosophy of Natural Science'

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10 ideas

4. Formal Logic / D. Modal Logic ML / 3. Modal Logic Systems / h. System S5
7791 The simplest of the logics based on possible worlds is Lewis's S5 [Lewis,CI, by Girle]
     Full Idea: C.I.Lewis constructed five axiomatic systems of modal logic, and named them S1 to S5. It turns out that the simplest of the logics based on possible worlds is the same as Lewis's S5.
     From: report of C.I. Lewis (works [1935]) by Rod Girle - Modal Logics and Philosophy 2.1
     A reaction: Nathan Salmon ('Reference and Essence' 2nd ed) claims (on p.xvii) that "the correct modal logic is weaker than S5 and weaker even than S4". Which is the greater virtue, simplicity or weakness?
7. Existence / A. Nature of Existence / 3. Being / a. Nature of Being
14664 Necessary beings (numbers, properties, sets, propositions, states of affairs, God) exist in all possible worlds [Plantinga]
     Full Idea: A 'necessary being' is one that exists in every possible world; and only some objects - numbers, properties, pure sets, propositions, states of affairs, God - have this distinction.
     From: Alvin Plantinga (Actualism and Possible Worlds [1976], 2)
     A reaction: This a very odd list, though it is fairly orthodox among philosophers trained in modern modal logic. At the very least it looks rather parochial to me.
9. Objects / D. Essence of Objects / 1. Essences of Objects
14666 Socrates is a contingent being, but his essence is not; without Socrates, his essence is unexemplified [Plantinga]
     Full Idea: Socrates is a contingent being; his essence, however, is not. Properties, like propositions and possible worlds, are necessary beings. If Socrates had not existed, his essence would have been unexemplified, but not non-existent.
     From: Alvin Plantinga (Actualism and Possible Worlds [1976], 4)
     A reaction: This is a distinctive Plantinga view, of which I can make little sense. I take it that Socrates used to have an essence. Being dead, the essence no longer exists, but when we talk about Socrates it is largely this essence to which we refer. OK?
10. Modality / A. Necessity / 2. Nature of Necessity
11002 Equating necessity with informal provability is the S4 conception of necessity [Lewis,CI, by Read]
     Full Idea: C.I.Lewis's S4 system develops a sense of necessity as 'provability' in some fairly informal sense.
     From: report of C.I. Lewis (works [1935]) by Stephen Read - Thinking About Logic Ch. 4
10. Modality / E. Possible worlds / 1. Possible Worlds / a. Possible worlds
14662 Possible worlds clarify possibility, propositions, properties, sets, counterfacts, time, determinism etc. [Plantinga]
     Full Idea: The idea of possible worlds has delivered insights on logical possibility (de dicto and de re), propositions, properties and sets, counterfactuals, time and temporal relations, causal determinism, the ontological argument, and the problem of evil.
     From: Alvin Plantinga (Actualism and Possible Worlds [1976], Intro)
     A reaction: This date (1976) seems to be the high-water mark for enthusiasm about possible worlds. I suppose if we just stick to 'insights' rather than 'answers' then the big claim might still be acceptable. Which problems are created by possible worlds?
10. Modality / E. Possible worlds / 1. Possible Worlds / d. Possible worlds actualism
16472 Plantinga's actualism is nominal, because he fills actuality with possibilia [Stalnaker on Plantinga]
     Full Idea: Plantinga's critics worry that the metaphysics is actualist in name only, since it is achieved only by populating the actual world with entities whose nature is explained in terms of merely possible things that would exemplify them if anything did.
     From: comment on Alvin Plantinga (Actualism and Possible Worlds [1976]) by Robert C. Stalnaker - Mere Possibilities 4.4
     A reaction: Plantinga seems a long way from the usual motivation for actualism, which is probably sceptical empiricism, and building a system on what is smack in front of you. Possibilities have to be true, though. That's why you need dispositions in actuality.
14. Science / D. Explanation / 1. Explanation / b. Aims of explanation
21507 Scientific explanation aims at a unifying account of underlying structures and processes [Hempel]
     Full Idea: What theoretical scientific explanation aims at is an objective kind of insight that is achieved by a systematic unification, by exhibiting the phenomena as manifestations of common underlying structures and processes that conform to testable principles.
     From: Carl Hempel (Philosophy of Natural Science [1967], p.83), quoted by Laurence Bonjour - The Structure of Empirical Knowledge 5.3
     A reaction: This is a pretty good statement of scientific essentialism, and structures and processes are what I take Aristotle to have had in mind when he sought 'what it is to be that thing'. Structures and processes give stability and powers.
19. Language / C. Assigning Meanings / 8. Possible Worlds Semantics
16469 Plantinga has domains of sets of essences, variables denoting essences, and predicates as functions [Plantinga, by Stalnaker]
     Full Idea: The domains in Plantinga's interpretation of Kripke's semantics are sets of essences, and the values of variables are essences. The values of predicates have to be functions from possible worlds to essences.
     From: report of Alvin Plantinga (Actualism and Possible Worlds [1976]) by Robert C. Stalnaker - Mere Possibilities 4.4
     A reaction: I begin to think this is quite nice, as long as one doesn't take the commitment to the essences too seriously. For 'essence' read 'minimal identity'? But I take essences to be more than minimal, so use identities (which Kripke does?).
16470 Plantinga's essences have their own properties - so will have essences, giving a hierarchy [Stalnaker on Plantinga]
     Full Idea: For Plantinga, essences are entities in their own right and will have properties different from what instantiates them. Hence he will need individual essences of individual essences, distinct from the essences. I see no way to avoid a hierarchy of them.
     From: comment on Alvin Plantinga (Actualism and Possible Worlds [1976]) by Robert C. Stalnaker - Mere Possibilities 4.4
     A reaction: This sounds devastating for Plantinga, but it is a challenge for traditional Aristotelians. Only a logician suffers from a hierarchy, but a scientist might have to live with an essence, which contains a super-essence.
19. Language / D. Propositions / 1. Propositions
14663 Are propositions and states of affairs two separate things, or only one? I incline to say one [Plantinga]
     Full Idea: Are there two sorts of thing, propositions and states of affairs, or only one? I am inclined to the former view on the ground that propositions have a property, truth or falsehood, not had by states of affairs.
     From: Alvin Plantinga (Actualism and Possible Worlds [1976], 1)
     A reaction: Might a proposition be nothing more than an assertion that a state of affairs obtains? It would then pass his test. The idea that a proposition is a complex of facts in the external world ('Russellian' propositions?) quite baffles me.