Modal realism
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Modal realism is the view, notably propounded by David Lewis, that possible worlds are as real as the actual world. It is based on the following notions: that possible worlds exist; possible worlds are not different in kind to the actual world; possible worlds are irreducible entities; the term "actual" in "actual world" is indexical.
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[edit] The term "possible world"
The term goes back to Leibniz' theory of possible worlds; used to analyze necessity, possibility, and similar modal notions. In short: the actual world is regarded as merely one among an infinite set of logically possible worlds, some nearer to the actual world and some more remote. A statement is called necessary if it is true in all possible worlds, and possible if it is true in at least one.
[edit] Main tenets of modal realism
At the heart of David Lewis's modal realism are six central doctrines about possible worlds:
- Possible worlds exist — they are just as real as our world;
- Possible worlds are the same sort of things as our world — they differ in content, not in kind;
- Possible worlds cannot be reduced to something more basic — they are irreducible entities in their own right.
- "Actual" is indexical. When we distinguish our world from others by claiming that it alone is actual, we mean only that it is ours — we live here.
- Possible worlds are unified by the spatiotemporal interrelations of their parts; possible worlds are spatiotemporally isolated from each other.
- Possible worlds are causally isolated from each other.
[edit] Discussion
In philosophy possible worlds are usually regarded as real but abstract possibilities. Some other times, as non-real, as a mere metaphor, abbreviation or façon de parler for sets of counterfactual propositions.
Lewis himself not only claimed to take modal realism seriously (although he did regret his choice of the expression modal realism), he also insists that his claims should be taken literally:
- "By what right do we call possible worlds and their inhabitants disreputable entities, unfit for philosophical services unless they can beg redemption from philosophy of language? I know of no accusation against possibles that cannot be made with equal justice against sets. Yet few philosophical consciences scruple at set theory. Sets and possibles alike make for a crowded ontology. Sets and possibles alike raise questions we have no way to answer. [...] I propose to be equally undisturbed by these equally mysterious mysteries." (David Lewis, Convention, 1968, p. 208)
- "How many [possible worlds] are there? In what respects do they vary, and what is common to them all? Do they obey a nontrivial law of identity of indiscernibles? Here I am at a disadvantage compared to someone who pretends as a figure of speech to believe in possible worlds, but really does not. If worlds were creatures of my imagination, I could imagine them to be any way I liked, and I could tell you all you wished to hear simply by carrying on my imaginative creation. But as I believe that there really are other worlds, I am entitled to confess that there is much about them that I do not know, and that I do not know how to find out." (David Lewis, Counterfactuals, 1973, pp. 87-88)
[edit] See also
[edit] References
- David Lewis, Counterfactuals, (1973 [revised printing 1986]; Blackwell & Harvard U.P.)
- David Lewis, Convention: A Philosophical Study, (1969; Harvard University Press)
- David Lewis, On the Plurality of Worlds (1986; Blackwell)
- David Armstrong, A Combinatorial Theory of Possibility (1989; Cambridge University Press)
- Colin McGinn, "Modal Reality" (Reduction, Time, and Reality, R.Healey [ed.]; Cambridge University Press)
