David Lewis, - PowerPoint PPT Presentation

About This Presentation
Title:

David Lewis,

Description:

'When I profess realism about possible worlds, I mean to be taken literally. ... The decisive objection to endurance is the problem of temporary intrinsics. ... – PowerPoint PPT presentation

Number of Views:455
Avg rating:3.0/5.0
Slides: 11
Provided by: brando6
Learn more at: https://www.uky.edu
Category:
Tags: david | endurance | lewis

less

Transcript and Presenter's Notes

Title: David Lewis,


1
David Lewis, Counterparts and Double Lives
  • Modal Realism
  • When I profess realism about possible worlds, I
    mean to be taken literally. Possible worlds are
    what they are, and not some other thing. If asked
    what sort of thing they are, I cannot give the
    kind of reply my questioner probably expects
    that is, a proposal to reduce possible worlds to
    something else.I can only ask him to admit that
    he knows what sort of thing our actual world is,
    and then explain that possible worlds are more
    things of that sort, differing not in kind but
    only in what goes on at them. (from
    Counterfactuals, p. 73)

2
Some fundamental theses of modal realism
  1. Possible worlds exist.
  2. Possible worlds are just like this one.
  3. Possible worlds are irreducible.
  4. Actual is an indexical expression.
  5. Possible worlds are unified by the spatiotemporal
    relations that its members have to each other.
  6. Possible worlds are causally isolated from one
    another.

3
Ersatz Modal Realism
  • Instead of an incredible plurality of concrete
    worlds, we can have one world only, and countless
    abstract entities representing ways that this
    world might have been. (PoW, 136)
  • Possible worlds are sets of possible
    individuals. One world/one set is actual (or
    actualized by God).
  • Linguistic ersatzism constructs its ersatz
    worlds as maximal consistent sets of sentences
    (PoW, 142)
  • Pictorial ersatzism presents possible worlds as
    pictures of individuals.
  • Magical ersatzism worlds have no relevant inner
    structure they are themselves simples (PoW, 174)

4
Good Questions and Bad
  • Is an F ever a G?
  • Is there ever identity between two worlds? I.e.
    do they overlap?
  • Is there ever anything that overlaps two
    different worlds? (Which is really a question
    about mereology is there any reason to restrict
    mereology?)
  • Does it ever happen that anything exists
    according to two different worlds?
  • But,
  • What is it for x to exist according to a world?
  • This question demands different answers
    depending upon whether one is a genuine modal
    realist or an ersatzer.

5
Counterpart Theory
  • Counterpart theory the theory that allows us to
    talk about individuals in other possible worlds
    that stand in the place of the members of our
    world.
  • Counterpart theorists and ersatzers are in
    agreement that there are other possible worlds in
    which Humphrey he himself really wins the
    election. Likewise, they are in agreement that
    Humphrey he himself is not part of those
    worlds.
  • For the counterpart theorist, the trick is to
    say that Humphrey names not the Humphrey of our
    world, and not the Humphrey of another, but
    rather the trans-world individual who is the
    mereological sum of all these local Humphreys.
    (157a)

6
Overlapping worlds and the problem of persistence
  • The problem of the overlap of worlds parallels
    the problem of identity through time. Let us say
    (160a)
  • Something persists iff, somehow or other, is
    exists at various times.
  • Something perdures iff it persists by having
    different temporal parts, or stages, at different
    times, though no one part of it is wholly present
    at more than one time.
  • Something endures iff it persists by being wholly
    present at more than one time.

7
  • Lewis favors perdurance in the case of identity
    through time and the parallel is to counterpart
    theory. That is, perdurance is analogous to the
    trans-world identity of a trans-world individual
    composed of distinct parts in non-overlapping
    worlds.
  • The decisive objection to endurance is the
    problem of temporary intrinsics.
  • The solution favored by Lewis is one in which
    there are distinct temporal parts of an
    individual that have different temporary
    intrinsic properties. (Presumably, we can talk
    about essentialism by saying that x is
    essentially F iff all temporal parts of x have F.
    Similarly, x is essentially F iff each of its
    counterparts is F.)

8
Unrestricted mereology
  • Lewis believes in unrestricted mereological
    composition any old class of things has a
    mereological sum. Whenever there are some
    things, no matter how disparate and unrelated,
    there is something composed of just those things.
    Even a class of things out of different worlds
    has a mereological sum. That sum is a
    trans-world individual. It overlaps each world
    that contributes a part of it, and so is partly
    in each of many worlds. (164b-65a)

9
  • If unrestricted composition is granted, Lewis
    can reformulate counterpart theory in terms of
    trans-world individuals. (166)
  • Now, check it out, some definition-mongering
  • A possible individual is an individual that is
    wholly part of one world.
  • If a possible individual X is part of a
    trans-world individual Y, and X is not a proper
    part of any other possible individual that is
    part of Y, let us call X a stage of Y.
  • Sometimes one stage of a trans-world individual
    will be a counterpart of another.
  • If all stages of a trans-world individual Y are
    counterparts of one another, let us call Y
    counterpart-interrelated.
  • If Y is counterpart-interrelated, and not a
    proper part of any other counterpart-interrelated
    trans-world individual (that is, if Y is maximal
    counterpart-interrelated), then let us call Y a
    -possible individual.

10
  • Extend the star language to predicates and
    properties. Thus,
  • A -possible individual is a -man at W iff it
    has a stage at W that is a man it -wins the
    presidency at W iff it has a stage at W that wins
    the presidency It -exists at world W iff it has
    a stage at W that exists (166b)
  • Two possible individuals are counterparts iff
    there is some -possible individual of which they
    both are stages. (167a)
  • Now, lets get rid of the stars.
  • In this way, counterpart theory can account for
    everything that the fan of trans-world identity
    wants.
Write a Comment
User Comments (0)
About PowerShow.com