Let's say that a man named Plato had a boat which he called the Ship of Theseus. Now, in the up-keep of this boat, Plato is forced to replace planks as they rot or become damaged. So, is it still the Ship of Theseus after he has replaced one plank? How about 5? Let us suppose that there are 100 planks on the boat, and that each day, our man Plato has to replace a single plank. Is it still the original Ship of Theseus at the end of the 100 days, after all of the planks have been replaced? If it is not, then at what point does it cease to be the original Ship, and become something different? 50 planks? More, or less?

My answer to this was that Yes, it would still be the original Ship of Theseus even after the hundred days, at which point none of the original planks would be present. As Plato replaces the planks, they become part of the boat. I argued that when the first plank was replaced, the new plank then became part of the original; thus, when the second plank was incorporated, it, too, became part of the original. Even the hundredth plank, which is being added to none of the original planks, is still part of the original, because all of the new planks which had been ad ded over time, had been part of the original boat. So, I concluded, after 100 days, the Ship was still the Ship of Theseus.

Suppose Plato disassembles the original Ship, then builds a new one, using the same plans, with all new materials. Is this still the Ship of Theseus?

My answer to this one was no. It may be a Ship of Theseus, but it isn't the original. Since none of the planks used had ever been part of the first, this would be a new boat. It may look the same, be a Theseus II if you will, but it is not the original boat.

Let's go back to the original question. Plato has the boat, and replaces the planks, one per day, until all of the wood is new. Let's just say that you agree with my theory, and that this boat that he has in his possession after the hundred days have passed is the original Ship of Theseus. Introduce character two, who will call Socrates. He sees what Plato is doing, and decides to make his own boat. So each day, as Plato discards his plank, Socrates takes the old plank, and adds it to his boat. Since he doesn't want to put out any more labor than is necessary, Socrates adopts the same design, and simply fits the plank into the same spot it had occupied on Plato's boat. Ok, so now, at the end of the 100 days, we have two boats. One of them is Plato's-brand new wood, same original design-and we have Socrates', which is identical to Plato's, and is, in fact, made out of the same original wood. Two boats, but only one to be called the Ship of Theseus. Which is it?

The great thing about philosophy is that you can change your answer as the facts change. Since there is never a correct answer, you can only give what you feel is the best answer, or the simplest. Now, I already said that, at the end of the hundred days, Plato still had in his possession the original Ship of Theseus. But now we have a second Ship made out of the original materials. So who has it now? In my mind, Plato's Ship is THE Ship until he replaces that last plank. At that point, Socrates completes his boat, and his then becomes the original Ship of Theseus. This may seem a bit odd, but let me explain. My initial theory still holds true, in that each new plank introduced becomes a part of the original. So, now we have a boat whose planks were all a part of the original. With the completion of Socrates' boat however, we now have the original-the same style, the same wood, all in their original places. This now becomes, for me, the better answer: Socrates' boat is the original Ship of Theseus.

Is your brain in a knot yet? No? Well then, riddle me this, Batman.
Aw...brain dead? Here, this should fix it....