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A Philosophical Conundrum

It’s Called “The Ship of Theseus”

It’s Called “The Ship of Theseus”

I got this puzzle from The Futility Closet, which I have decided to add to my links:

Suppose we have a complete wooden ship, and one day we replace one of its wooden planks with an aluminum one. Most people would agree that the ship survives this operation; that is to say, its identity remains unchanged. But suppose that we then replace a second plank, and then a third, until our wooden ship is made entirely of aluminum. Is this the same ship that we started with? If not, when did it change?

Thomas Hobbes adds a wrinkle: Suppose that, as we did all this refurbishing, someone had gathered up all the discarded wooden planks and used them to assemble a second ship. What are we to make of this? “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.”

And philosopher Roderick Chisholm adds another: “Let us suppose that the captain of the original ship had solemnly taken the vow that, if his ship were ever to go down, he would go down with it. What, now, if the two ships collide at sea and he sees them start to sink together? Where does his duty lie — with the aluminum ship or with the reassembled wooden ship?”


3 thoughts on “A Philosophical Conundrum

  1. True life example.

    In the late ’60s, I purchased a Parker 41 fountain pen. Over the years, I’ve sent it in for repairs (heat out here is bad for the plastic and the rubber? ink reservoir). Someone from Parker called me the last time I sent it in (about 5 or 6 years ago) to say the pen could no longer be repaired–no more replacement parts left in inventory as the pen was so old.

    I made a comment then about the Parker 41, and I was told that the only part remaining from the original pen was the cap. Over the years everything else had been replaced, and replaced from identical parts from similar versions of that pen.

    Is this the same pen I started out with? If not, when did it change?

    Side note: Since the pen could no longer be repaired, I decided to satisfy my curiosity and took the pen apart. There were more little pieces in there than I expected. Once I got it apart, I looked carefully at the parts and couldn’t see where the problem might be (the pen leaked).

    I decided to see if I could put it back together and succeeded–so much so that I didn’t have any parts left over (what usually happens to me). Curious again, I filled it up and it no longer leaked. I guess some of those small parts had gotten out of alignment, and I accidentally solved the problem. Apparently, the repair person at Parker was used to replacing parts and never thought about trying to fix it.

    I am still using the pen to this day.

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