On 19 Jul 2016, at 06:58, Bruce Kellett wrote:
On 19/07/2016 2:18 am, Bruno Marchal wrote:
On 18 Jul 2016, at 03:54, Bruce Kellett wrote:
As you say in another post, computationalism depends on the
breakdown of transitivity for personal identity: M is the same as
H; W is the same as H; but M is not the same as W. Given this, you
have all sorts of problems with the nature of personal identity --
maybe it is not a modal concept! I will talk more about this in
reply to your other post.
Well, the machine notion of 3p-self can be defined in arithmetic,
and all correct machine knows that her 1p-self is not. Sure it is a
tricky notion, but the non transitivity is not a problem, as the
"Parfit person series" will work transitively in all cases, except
when duplication occurs, but why would that cause any problem, you
tell me. Nothing here threats the validity of the reasoning leading
to the reversal physics/arithmetic. I think you confused non
transitivity (the failing of some transitive link) with
intransitivity (the failing of all transitive link). With self-
duplication, we lost transitivity in one case, but both surviver
recover it as long as they do'nt duplicate again, and so the old
guy who stayed in Moscow remains the same young guy who teleported
at Moscow through some duplication a long time ago. You might
elaborate on your problem, as I don't see any.
I think a relation is either transitive or it is intransitive:
personal identity is a transitive relation; 'father of' is an
intransitive relation. You can't be 'half-pregnant', as it were.
I quote from Wikipedia on personal identity:
"Generally, personal identity is the unique numerical identity of a
person in the course of time. That is, the necessary and sufficient
conditions under which a person at one time and a person at another
time can be said to be the same person, persisting through time."
And from the Internet Encyclopedia of Philosophy: www.iep.utm.edu/person-i/
"Personal identity is an instance of the relation of numerical
identity; investigations into the nature of the former, therefore,
must respect the formal properties that govern the latter. The
concept of identity is uniquely defined by (a) the logical laws of
congruence: if X is identical with Y, then all non-relational
properties borne by X are borne by Y, or formally "A(x,y)[(x = y) --
> (Fx = Fy)]; and (b) reflexivity: every X is identical with itself,
or formally "Ax(x = x). (Note that congruence and reflexivity entail
that identity is symmetric, "A(x,y)[(x = y) --> (y = x)], and
transitive, "A(x,y,z)[((x = y) & (y = z)) --> (x = z)]."
And later in the same article:
"Should fission be an acceptable scenario, it presents problems for
the psychological approach in particular. The fission outcomes Y1
and Y2 are both psychologically continuous with X. According to the
psychological approach, therefore, they are both identical with X.
By congruence, however, they are not identical with each other: Y1
and Y2 share many properties, but even at the very time the fission
operation is completed differ with regard to others, such as spatio-
temporal location. Consequently fission cases seem to show that the
psychological approach entails that a thing could be identical with
two non-identical things, which of course violates the transitivity
of identity."
Fission, in this case, is equivalent to the duplication protocols
under consideration in this discussion. There does not seem to be
any widely agreed resolution of the problems that the duplication
scenarios entail. Some acknowledge that these scenarios indicate
that psychological continuity is not sufficient for person identity.
"These commentators typically complement their psychological theory
with a non-branching proviso and/or a closest continuer clause. The
former states that even though X would survive as Y1 or Y2 if the
other did not exist, given that the other does exist, X ceases to
exist." This might be problematic, however, and we could avoid some
problems by adding a closest-continuer or best candidate clause,
stating roughly that the best candidate for survival in a
duplication scenario, that is, the duplicate which bears the most or
the most important resemblances to the original person X, is
identical with X." For instance, if the original survives the
duplication, he is the closest continuer and hence uniquely
identical to the original.
And so on. As I have said, the philosophical literature on personal
identity is extensive and quite complex. The idea of transitivity of
personal identity does seem to be central, so duplication cases are
often problematic.
Parfit's analysis seems to suggest that the duplication scenarios,
since they violate transitivity, entail that the original that is
being duplicated does not survive the duplication. However, in the
duplication case with two copies, Y1 and Y2, although the original X
dies, having two survivors identical to the original is even better
that being identical to just one survivor. "Generally, according to
Parfit, psychological continuity with any reliable cause matters in
survival, and since personal identity does not consist merely in
psychological continuity with any reliable cause, personal identity
is not what matters in survival."
Whatever line one takes with respect to personal identity in
general, and in duplication cases in particular, it seems clear that
the simple psychological account of personal identity is
insufficient to survive all the difficulties. Abandoning the
transitivity of identity is difficult in general because it is
precisely that transitivity that gives us a reliable notion of the
continuity of personhood through time. The things that might seem to
violate transitivity in duplication (copies in separate locations,
etc, that is, non-psychological differences), also would give
violations of transitivity relating copies of the same person at
different times and places. We need a principled account of exactly
what leads to the violation of transitivity in one case and not in
the other. That is why I still think that the original is the
continuation if not deleted during duplication, and the duplicate in
that case is simply a new separate person -- sharing some background
and memories with the original, for sure, but actually a different
person. Identical twins can share many memories and other
characteristics without us ever thinking that they are two copies of
the same person. If the original is deleted during duplication, then
two new distinct individuals are created.
In this way, the important principles of identity, such as
congruence and transitivity, are respected in all cases.
But then computationalism is made false. With computationalism, or
with Everett, the duplication illustrates the non transitivity of 1p
identity. There is no problem with this, other than eventually
justifying the physical laws by arithmetical self-reference. And this
is confirmed by the fact that the logic of alternatives continuation
in that frame gives exactly what we expect: a quantum logic.
Bruno
Bruce
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