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The Ship of Theseus 89 |
[I]f, for example, that ship of Theseus, concerning the difference whereof |
made by continual reparation in taking out the old planks and putting in new, |
the sophisters of Athens were wont to dispute, were, after all the planks were |
changed, the same numerical ship it was at the beginning; and if some man |
had kept the old planks as they were taken out, and by putting them afterwards |
together in the same order, had again made a ship of them, this, without |
doubt, had also been the same numerical ship with that which was at the |
beginning; and so there would have been two ships numerically the same, |
which is absurd. (Hobbes Chapter 11, 136) |
P1. T1 is identical with T2. |
P2. It is not the case that T2 is identical with T3. |
P3. T3 is identical with T1 (assumption for reductio ). |
C1. T3 is identical with T2 (transitivity of identity, P1, P3). |
C2. T2 is identical with T3 (symmetry of identity, C1). |
C3. It is not the case that T2 is identical with T3 and T2 is identical with |
T3 (conjunction, P2, C2). |
C4. It is not the case that T3 is identical with T1 (r eductio , P3 β C3). |
23 |
The Problem of |
Temporary Intrinsics |
Montserrat Bordes |
Lewis , David . On the Plurality of Worlds . Oxford : Blackwell , 1986 . |
Lowe , E. J. β The Problems of Intrinsic Change: Rejoinder to Lewis . β Analysis |
48 ( 1988 ): 72 β 7 . |
Moore , G. E. Philosophical Studies . London : Oxford University Press , 1922 . |
Our pre - theoretic beliefs tell us that ordinary things such as trees, people, |
or chairs change their properties during their existence. We can say that |
ordinary things persist β they exist at different times β and change; that is, |
they persist and have complementary properties (P, not - P) at distinct times. |
What remains controversial, however, is the way in which ordinary things |
persist. We commonly distinguish between ordinary things and events. |
Some think that unlike football games, weddings, and smiles, ordinary |
things persist by having only spatial, not temporal parts; they appear to |
endure rather than perdure. Something endures if and only if it persists by |
being wholly present at different times; something perdures if and only if |
it persists by having distinct temporal parts at different times (Lewis). |
Opponents of endurantism think that ordinary things endure, whereas their |
histories, which are types of events, perdure (Lowe). Perdurantists hold that |
both events and ordinary things have not only three spatial dimensions but |
also a temporal one: they have (the worm view) or are (the stage view) |
temporal parts. |
Just the Arguments: 100 of the Most Important Arguments in Western Philosophy, |
First Edition. Edited by Michael Bruce and Steven Barbone. |
Β© 2011 Blackwell Publishing Ltd. Published 2011 by Blackwell Publishing Ltd. |
The Problem of Temporary Intrinsics 91 |
Is there a rationale for preferring one theory of persistence to another? |
Lewis thought that the argument from temporary intrinsics (ATI) shows |
compellingly that endurantism is untenable. His reasoning can be presented |
as follows. Ordinary things undergo change of their temporary intrinsic |
properties; that is, they gain or lose (monadic) properties, that they have in |
virtue of the way they themselves are, not in virtue of their relations to |
other things. Put differently, A β s intrinsic properties are properties shared |
by every duplicate of A (Moore and Lewis). |
Endurantist and perdurantist explanations of change are incompatible. |
To illustrate this, let us suppose that A is P at time t and that A also |
existed at a past time t β when A was not - P. For a perdurantist, this amounts |
to A β s having a temporal part that is P at t and A β s having another part |
that is not - P at t β . For an endurantist, A itself (not a proper part of it) is |
P at t and not - P at t β . Supporters of endurantism, then, face a contradiction, |
that A itself is both P and not - P, that is also at odds with Leibniz β |
Law of the Indiscernibility of Identicals: given that A endures from t β to |
t , A must therefore be the same from t β to t (A at t β is diachronically |
identical to A at t ), and A should have the same properties at both |
times (A at t β should be indiscernible from A at t ). Lewis states that endurantism |
cannot account for the existence of temporary intrinsic properties |
demanded by ATI, since the efforts to solve the contradiction deny either |
the nonrelational nature of properties, their instrinsicality, or their |
temporality. |
P1. Ordinary things change their intrinsic properties (properties that ordinary |
things have in virtue of the way they themselves are, not in virtue |
of their relations to other things). |
P2. Properties can be either of two mutually exclusive types: extrinsic or |
intrinsic. |
P3. If ordinary things change their intrinsic properties, then ordinary things |
persist; that is, they exist at different times. |
C1. Ordinary things persist ( modus ponens , P1, P3). |
P4. If ordinary things persist, then they either endure (persist by being |
wholly present and numerically identical at more than one time) or |
perdure (persist by having temporal parts or being partially present at |
more than one time). |
C2. Ordinary things either endure or perdure ( modus ponens , P4, C1). |
P5. Indiscernibility (having the same intrinsic properties) is a necessary |
condition of numerical identity (the Law of Indiscernibility of Identicals |
implied by Leibniz β Law). |
P6. If ordinary things endure, then ordinary things cannot remain numerically |
identical if they have incompatible (like P and not - P) intrinsic |
properties (general instantiation, P5). |
92 Montserrat Bordes |
P7. If ordinary things cannot remain numerically identical if they have |
incompatible properties, then either intrinsic properties are either disguised |
relations to times or the only intrinsic properties of ordinary |
things are those they have in the present. |
C3. If ordinary things endure, then either intrinsic properties are either |
disguised relations to times or the only intrinsic properties of ordinary |
things are those they have in the present (hypothetical syllogism, P6, |
P7). |
P8. If ordinary things perdure, then their incompatible properties belong to |
different things (i.e., their different temporal parts). |
P9. If intrinsic properties are disguised relations to times, then all properties |
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