Geez, isn't philosophy wonderful?
What follows is a debate I participated in about this paradox- several years ago- on the Atlantis mailing list.
To: [email protected]
Subject: OWL: Re: The ship(s) of Theseus
Date: Saturday, August 07, 1999 12:10 PM
ABSTRACT: My two cents, for whatever they're worth: As I understand
it, the "ship of Theseus" paradox is as follows: While the ship is being
upgraded, plank by plank, another identical ship is being constructed
from the discarded planks. When the ship that is being constructed from
the discards is finished, it will be identical to the original ship before
the original was upgraded. So the question is: which of the two ships is
"the ship of Theseus" -- the one constructed from the discards, or the one
that is upgraded? At the risk of adding nothing essentially new to the
discussion, I will attempt an answer, realizing full well that many other
thoughtful answers have already been given.
------------------------------------
Let us suppose that instead of a second ship's being constructed, the
discarded planks were burned as firewood. (Steve Hreczkosij presents
the paradox as if this were the actual story, but as I understand it, the
old planks were used to build another ship.) At any rate, would the
upgraded ship composed of the new material be the same ship as the
original before the latter was upgraded? Or would it be an entirely
different ship? Once we answer this question, we will be in a better
position to solve the paradox.
In one sense, the upgraded ship is the same as the original, just as I
am the same person as I was 50 years ago. It is in this sense that the
upgraded ship is still the same ship. To be sure, the ship has changed,
but as (I think) Aristotle pointed out, in order for something to change,
it must in some sense remain the same throughout the process of change.
Otherwise, there would be nothing to UNDERGO the process of change. If
the thing that changed were not in some sense the same after the change
as before, then what you would have is not CHANGE but REPLACEMENT.
There is thus a difference between upgrading the ship of Theseus, and
replacing it with an entirely new and different ship.
It may be objected that if every plank of the ship has been replaced, then
the ship itself has been replaced, in which case, you DO have an entirely
new and different ship. But every plank OF WHAT has been replaced?
Of "the ship", obviously -- which means of the SAME ship. To deny
sameness on the grounds of change is therefore self-refuting, because
change PRESUPPOSES sameness. For change to occur, SOMETHING
(the same thing) must change.
Consequently to deny identity in virtue of change a la Heraclitus is
to commit "the fallacy of the stolen concept". It is to "steal" the
concept of 'change' -- a concept to which one has no epistemological
right, if one denies the concept of 'identity' on which it logically and
genetically depends. (For an excellent discussion of this fallacy, see
"The Stolen Concept" by Nathaniel Branden in the January 1963 issue
of _The Objectivist Newsletter_.)
Since we see that there is a spatio-temporal continuity to the ship as it
undergoes an upgrade, we are able to differentiate its subsistence in a
changed form from its replacement by something with a different identity.
Thus, we can say with assurance that the upgraded ship is in some
sense the same ship as it was before it was upgraded, just as I am
the same person as I was 50 years ago, even though my cells are different.
Now we may return to the second ship, which is being constructed from
the discarded planks of the original, and answer the question whether
or not THAT ship is the "same" ship as the original. We can see that
when the newly constructed ship is fully built, it will be identical in
structure and material to the original ship. Therefore, it is difficult to
see how it too couldn't be regarded as "the same ship". So what is
the difference between it and the upgraded ship? Are they both "the"
ship of Theseus?
Well, the upgraded ship is NOT the same as the original *in respect to
its material*. In that sense, it is an entirely different ship -- just as
in respect to my cells, I am an entirely different person than I was 50
years ago. Conversely, the newly constructed ship made from the
original planks IS the same as the original ship *in respect to its
material and structure*. (Of course, the original planks will be a little
older -- a little more worn -- than they were when they were part of the
original ship, so in that sense, they're not exactly the same material
either, although they are the "same" in the sense that the upgraded ship
is the "same".)
Consequently, where there was only one ship "of Theseus", there are
now two -- each being the "same" as the original ship, albeit *in different
respects*. There is nothing contradictory about this conclusion. Both
are "ships of Theseus". Clearly, the upgraded ship is the original ship
with new planks, and the reconstructed ship is the original ship with the
original planks -- which is no more paradoxical than saying that the
original ship was the ship of Theseus and that the upgraded ship (which
is clearly different from the original ship) is also the ship of Theseus.
Rick
_________________________________________________________________________________________________________
From: Gayle Dean
To: [email protected]
Subject: OWL: Re: The "Fleet" of Theseus
Date: Wednesday, August 11, 1999 3:02 PM
ABSTRACT:
At the moment we have two ships -- Ship A is the original ship
of Theseus which has been completely updated over time with
all new parts. Ship B is the reconstruction of the ship using
the old-worn parts removed from ship A, as it was upgraded.
Bill Dwyer has used two different arguments, together -- to support
his conclusion that the two "Ships of Theseus" are the same ship.
This raises some interesting questions.
1. Bill says that due to spatio-temporal continuity (STC) (a persisting
object tracing a continuous path through space-time changing it's parts
gradually while preserving the form of the object) "we can say with
assurance that the upgraded ship [A] is in some sense the same
ship as it was before it was upgraded," just as he is the same person
he was 50 years ago, even though his cells are different...that STC
is sufficient to establish Ship [A] as the "Ship of Theseus."
2. He also says that because ship B is reconstructed of exactly
the same (old worn) parts as the original, arranged in the same form
that "material and form" is also sufficient to establish Ship B as the
"ship of Theseus."
And he concludes: "...where there was only one ship "of Theseus",
there are now two -- each being the "same" as the original ship, albeit
*in different respects*." And he says there is nothing contradictory
about his conclusion that both are "ships of Theseus".
I'm not clear in what "sense" he means that both are "ships of Theseus".
But, I understood the question to be a question of identity -- "which"
ship has "identity" as the ship of Theseus? That said, I'll continue:
We now have Ship A the updated ship and Ship B the reconstructed
ship...both *the* "ships of Theseus." But, what if, once again, we
slowly replace the planks of the upgraded ship A and use its newly
discarded planks to create a third Ship C. We will then have two
old reconstructed ships in our warehouse -- ship B and ship C --
plus the one ongoing upgraded ship A. And in fact, we could spawn
an entire "Fleet of Theseus" from the original ship in this way --ships
A through Z. But, are they really all the same ships of Theseus?
According to the two arguments above they would be. But, using
those two criteria to establish identity of a ship, gets even more
complicated.
What if we replace the parts of the original ship of Theseus, over
time-- not with newly manufactured parts -- but, instead with parts
from a sister ship, say, the "Ship Of Fools" which is being sold off
piece-by-piece because the owner is upgrading it with mahogany.
What happens when all the parts of the ship of Theseus have been
completely replaced with the parts from the upgraded Ship of Fools?
Does the Ship of Fools become the Ship of Theseus? Or do the two
ships share identities? After all, the reconstructed Ship of Fools has
now taken on the same "material and form" that it possessed earlier,
but in the "ghost"of the Ship of Theseus...while at the same time, the
Ship of Theseus has persisted over time during its upgrading. Or would
there be two "Ships of Fools" sailing simultaneously...the newly
upgraded mahogany one that meets the STC criteria and the reconstructed one
in the body of the ship of Theseus which meets the "material and form"
criteria. And what becomes of the Ship of Theseus?
I'm not convinced that either the "spatio-temporal continuity" theory
or the "material and form" theory answers this paradox. And it would
seem that perhaps, the best way to establish *which ship* is the
actual Ship of Theseus, would be to ask Theseus. He would say
that the ship on which he is currently sailing is in fact, the "Ship of
Theseus"and the old reconstructed ships taking up space in the
warehouse are the "OLD" Ships of Theseus...clearly separate and
distinct vessels...all 26 of them:-)
And of course the upgraded mahogany "Ship of Fools" that Katherine
Anne Porter is now sailing would be the real "Ship of Fools."
Gayle Dean
_________________________________________________________________________________________________________
From: "William Dwyer"
To: <[email protected]>
Subject: OWL: Re: The "Fleet" of Theseus
Date: Sunday, August 15, 1999 1:24 PM
Gayle Dean makes an excellent contribution to one version of the "ship of
Theseus" problem in her recent post "The 'Fleet' of Theseus" by
highlighting the paradox in a dramatic way. Let me see if I can address
her points.
I had argued that if a second ship were reconstructed out of materials
discarded from the Ship of Theseus when and as the latter was being
upgraded, then the second ship would also qualify as "the Ship of Theseus",
if only in a different respect from the first.
But Gayle says that if one can create a second ship with the same identity
as the first, then one can create a third ship with the same identity as
the second, etc., until one has an entire fleet of ships in which each and
every ship is "the Ship of Theseus".
Yes, this would follow logically from my solution; every ship in the fleet
would be "the Ship of Theseus" -- but again, *in different respects* --
however absurd that may seem! :)
Nevertheless, Gayle identifies another, even more paradoxical implication
of my theory. She states:
> What if we replace the parts of the original ship of Theseus, over
> time-- not with newly manufactured parts -- but, instead with parts
> from a sister ship, say, the "Ship Of Fools" which is being sold off
> piece-by-piece because the owner is upgrading it with mahogany.
> What happens when all the parts of the ship of Theseus have been
> completely replaced with the parts from the upgraded Ship of Fools?
> Does the Ship of Fools become the Ship of Theseus? Or do the two
> ships share identities?
Yes, very interesting! Well, I would have to say, based on my analysis,
that the upgraded Ship of Theseus is still the "same" ship, albeit in a
renewed form. But I would also have to say that in another respect, that
very same ship is also the Ship of Fools, since it now has that particular
ship's form and material. It is the Ship of Fools, because all we have
done to the latter, in effect, is disassemble and reassemble it.
So what we have, then, is one ship with two identities. In one respect,
the ship is still the Ship of Theseus in an upgraded form, but in
another respect, it is the reassembled Ship of Fools. Weird, huh!
> I'm not convinced that either the "spatio-temporal continuity" theory
> or the "material and form" theory answers this paradox.
Well, a paradox is an apparent contradiction. Resolving it consists of
explaining why there is in fact no contradiction. I don't think there's a
contradiction in claiming that there are two ships in the form of one,
if they are different ships *in different respects*. It would only be a
contradiction if they were considered different ships at the same time
and in the *same respect*.
But I will grant that my solution does seem logically odd, and for that
reason may not be entirely satisfying. So I must credit Gayle with an
ingenious example. (One philosopher I read -- I can't remember who --
believes that only the upgraded ship is the same ship; not the
reconstructed ship, which, if he is correct, would mean that there is
no Ship of Fools "in" the Ship of Theseus. But I don't find his solution
entirely satisfying either.)
> And it would seem that perhaps, the best way to establish *which ship*
> is the actual Ship of Theseus, would be to ask Theseus.
Here I don't agree. Theseus could be mistaken. But in my opinion, it
doesn't have to be either/or. It can be both, but not at the same time and
in the same respect.
Nevertheless, I would encourage Gayle to submit her discussion to a
philosophy journal (perhaps _Mind_) as she may have an original
contribution to make to the way that this problem is conceived and
presented.
Bill Dwyer
___________________________________________________________________________________________________________
From: "Gayle Dean" <[email protected]>
To: <[email protected]>
Subject: Re: The Fleets of "Infinite Replication:" Reply to Dwyer
Date: Monday, August 16, 1999 11:38 AM
Bill Dwyer apparently enjoyed my disagreement with him over
the identity of the 'Fleet of Theseus,' but he gives me too much
credit for creativity in presenting the problem. In my study of
philosophical paradoxes, I'm sure I've seen these examples used
by others in some form or another. But, thanks to Bill for his
expression of confidence -- it's always a delight to hear that "the
second best mind on the list" recognizes one's own mind as
"ingenious.":-)
However, I must continue to disagree with Bill's "same ship, different
respects" resolution of these paradoxes. Earlier he claimed that, we
could have many different ships, all with the same identity and now he
claims that we can have one ship with two identities. He says:
>Yes, very interesting! Well, I would have to say, based on my
>analysis, that the upgraded Ship of Theseus is still the "same" ship,
>albeit in a renewed form. But I would also have to say that in another
>respect, that very same ship is also the Ship of Fools, since it now
>has that particular ship's form and material. It is the Ship of Fools,
>because all we have done to the latter, in effect, is disassemble
>and reassemble it. So what we have, then, is one ship with two
>identities. In one respect, the ship is still the Ship of Theseus in
>an upgraded form, but in another respect, it is the reassembled
>Ship of Fools. Weird, huh!
Now I can imagine that ancient mariners who believed the earth was
flat -- upon seeing ships sail off "over the edge" only to reappear
again later in perfect condition -- might have had the same reaction.
But, "Weird, huh!" is not an argument :-)
So, essentially Bill is saying that he stands by the idea that the
"spacial-temporal-continuity" and "mereological theory of identity"
(MTI) are correct theories for establishing the identity of ships.
So let's inventory: We now have 26 *physical ships* A through Z
in the warehouse all with the same identity as the Ship of Theseus,
and we also have one *physical ship* sailing the oceans with 2
different identities (the Ship of Theseus and the Ship of Fools).
And let's not forget the *other* upgraded mahogany "Ship of Fools"
resting at the pier. But Bill says:
>I don't think there's a contradiction in claiming that there are two
>ships in the form of one, if they are different ships *in different
>respects*. It would only be a contradiction if they were considered
>different ships at the same time and in the *same respect*.
But, this gets too complicated. Because, just as we were able to
repair the original Ship of Theseus with the planks from the
upgraded Ship of Fools, we can easily upgrade 'Theseus/Fools'
again as she ages, with new planks from a third sister ship the
"Ship of Infinite Replication" that has also decided to upgrade --
thus giving us one ship, now with three identities...!
So we can have the 26 ships in the warehouse that are ALL the
*same ship of Theseus* but in *different respects.* And at the
same time we can have one *single mongrel ship* sailing the
seas with the identities of an unlimited number of other ships living
in its *one form,* all of course in *different respects*?
"Respectfully," I must say that Identity is getting awfully crowded:-))
Gayle Dean
"It has long been an axiom of mine that the little things are infinitely
the most important." Sir Arthur Conan Doyle