|Cross-world identity, philosophy: is an expression for the problem of how to determine the identity of an object by accepting properties that it does not have in the actual world. Is it meaningful to say that Paul could have been taller in a possible world than he actually is, or would Paul be another individual then? See also possible worlds, modal realism, counterpart theory, counterpart relation, counterparts, telescope theory, centered worlds.|
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Cross-world identity/Hintikka: cross-world identity remains a crucial problem. Thesis: it is to trace an object (or its trace) in the worlds that it has in common.
That is, it boils down to a re-identification, between time slices of the same event development. It is a matter of continuity.
The problem corresponds to the stability theory of sets of differential equations.
Catastrophe theory/René Thom/Hintikka: the problem is closely related to the catastrophe theory.
Quine: considers it a hopeless problem.
HintikkaVsKripke: he underestimates the problem and considers it to be guaranteed. He cheats.
Worldline/Cross-World Identity/Hintikka: 1. We must allow that some objects not only exist in certain possible worlds, but that their existence is unthinkable there! That is, world lines can cease to exist - even worse: it may be that they are not defined in certain possible worlds.
Problem: this is not permitted in the usual knowledge logic (religious logic).
2. World lines can be drawn in two ways:
Analogy: this can be related to Russell's distinction between knowledge through acquaintance and description.
Cross-world identity/Hintikka: Problem: e.g. the problem can be an intentional (opaque) context (belief contexts). Here the existential generalization (EG) fails. That is, if a sentence A[b] is true for a subject, we cannot conclude that there is an object from which the sentence A is true (Ex) A [x].
Solution/semantics of possible worlds/Hintikka: the solution is to accept different individuals in different worlds. If the semantics of possible worlds is right, we somehow manage to determine the cross-world identity.
Knowledge/knowledge-who/knowledge-what/semantics of possible worlds: E.g.
(4) (Ex) Victoria knows that Lewis Carroll is x.
Model-theoretically, this means that "Lewis Carroll" picks out the same individual in all the worlds that are compatible with Victoria's knowledge.
This is synonymous with
(5) Victoria knows who Lewis Carroll is.
Possible Worlds/Universe/Cross-World Identity/HintikkaVsLeibniz/Hintikka: Problem: when worlds are whole universes, the framework between them changes too often that it is questionable how to re-identify individuals.
Cross-world identity/cross-world identification/Hintikka: normally we hold a large part of the world fixed when we identify two individuals.
Comparability Hintikka/(s): thus alternatives become comparable. To make alternatives to different parts comparable, we extend them. The extensions should have a part in common.
In an extreme case, they share their story. Identical: two individuals are indentical when their story coincides. This leads to the fact that cross-world identification is partially reduced to re-identification. That is, it becomes the problem. How space-time can be traced back to a common basis.
Advantage: we do not have to consider every single possible world.
Cross-world identification/cross-world identity/Locke/Kripke/Hintikka: Thesis: Causation plays an important role.
Cross-world identification/cross-identification/perception/Hintikka: here we have to assume a situation when it comes to perceptual identification. For there must be in them a perceptible, and the different situations (worlds) must share the perception space of the subject.
Semantics of possible worlds/perception/HintikkaVsSemantics of possible worlds: Hintikka has overlooked this point.
Situation/semantics of possible worlds/Hintikka: Furthermore, the semantics of possible worlds should investigate relations between smaller and larger situations.
Descriptive cross-world identification/descriptive/Hintikka: descriptive identification should take place between parts of the world that are larger than the actual perceptual cross-identification. So a comparison between "bigger" and "smaller" situations.
Jaakko and Merrill B. Hintikka
The Logic of Epistemology and the Epistemology of Logic Dordrecht 1989
J. Hintikka/M. B. Hintikka
Untersuchungen zu Wittgenstein Frankfurt 1996