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Reidentifying the Ship of Theseus

September 2, 2011

In my metaphysics class we have to write one 2-page paper each week.  This is my paper which I turned in last week.  I’ll post each of my papers on here throughout the semester.  This will help my blog become more cohesive.  Don’t fret if you don’t understand or find the posts boring.  While I didn’t do so with the essay below, I’ll try to make them more reader friendly from now on.  It’s difficult to do so with such logical outlining (a requirement for the class), but I’ll try nonetheless. Also, I’ll probably be posting Philosophy of Religion essays and thesis work as well.  Those should be a bit more enjoyable to read.

*Begin Essay*

In “How to Reidentify the Ship of Theseus”, the problem is one of identity. At the start, Bombos brings his ship, X, in for repair at dock A[1]. Ship X is made up of 1000 old planks. It will be repaired with 1000 new planks. Upon completion of repairs, the ship in dock A (presently X) will be called ship Y. Additionally, Morion orders a ‘new’ ship, Z, which will be constructed out of 1000 used planks at dock B. The construction process is as follows: One plank is removed from ship X in dock A each hour and replaced by a new plank, while the removed plank is placed in dock B as a part of ship Z. After 1000 hours of labor, ships Y in dock A and Z in dock B are completed.

The problem arises when ship Z is destroyed. An argument ensues over who might take ownership of ship Y in dock A. Bombos claims ownership of the ship due to the fact that it has occupied the same space-time line as ship X, his original ship, and Morion claims ownership due to the fact that is compiled of new parts and is thus a ‘new’ ship, just as he ordered. The concluding argument for ownership of the ship is as follows:

1. Ship X is in ownership of Bombos

2. Ship X is comprised of 1000 planks

3. Every hour, one plank is removed from ship X in dock A and replaced by a new plank

4. Every hour, the removed plank is placed onto ship Z

5. Ship Y is the product of 1000 new planks having been placed on ship X

6. After 1000 hours ship Y stands in dock A (3 and 5)

7. The identity of a ship is knowable by the identity of its parts

8. Ship X is composed of ‘currently parts of ship X’

9. Any plank removed from ship X is considered one of ‘previously parts of ship X’

10. ‘Previously parts of ship X’ are not equal to ‘currently parts of ship X’ (8 and 9)

11. Ship Z is composed of ‘previously parts of ship X’ (4 and 9)

12. Ship Z cannot be identified as ship X (7,8,10,11)

13. Ship Y is composed of ‘currently parts of ship X’

14. Ship X is identical with ship Y (8 and 13)

15. Ship Y is in ownership of Bombos (1 and 12)

This argument, and the article as a whole, aids in problems with identity. However, the conclusion of the argument is largely based on the fact that planks were replaced one by one. What if the planks were replaced two by two or three by three? Even more so, what if the planks were replaced five hundred by five hundred? There would seem to be a real problem as to the identity of ship X if the latter were the case. Thus, in this argument, the identity of an entity seems to be distinguished by the majority of its parts at one time.


[1] Smart, Brian. “How to Reidentify the Ship of Thesus.” Analysis, Vol. 32, No. 5 (Apr., 1972), pp. 145-148. Oxford University Press. http://www.jstor.org/stable/3327760

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From → Philosophy

2 Comments
  1. The movie 21 Grams explores this problem in relation to human beings. A character in the movie receives a heart transplant and then has an affair with the donor’s wife.

    • Interesting. We discussed personal identity this past week.

      The main question was, “what would happen if you transplanted two halves of one person’s brain into separate bodies?”

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