User:ZyrettiSpaghetti/Theseus

Ship of Theseus[edit]
Main article: Ship of Theseus

According to Plutarch's Life of Theseus, the ship Theseus used on his return from Minoan Crete to Athens was kept in the Athenian harbor as a memorial for several centuries."'The ship wherein Theseus and the youth of Athens returned had thirty oars, and was preserved by the Athenians down even to the time of Demetrius Phalereus, for they took away the old planks as they decayed, putting in new and stronger timber in their place…'"The ship had to be maintained in a seaworthy state, for, in return for Theseus's successful mission, the Athenians had pledged to honor Apollo every year henceforth. Thus, the Athenians sent a religious mission to the island of Delos (one of Apollo's most sacred sanctuaries) on the Athenian state galley—the ship itself—to pay their fealty to the god. To preserve the purity of the occasion, no executions were permitted between the time when the religious ceremony began to when the ship returned from Delos, which took several weeks.

To preserve the ship, any wood that wore out or rotted was replaced; it was thus unclear to philosophers how much of the original ship remained, giving rise to the philosophical question of whether it should be considered "the same" ship or not. Such philosophical questions about the nature of identity are sometimes referred to as the "Ship of Theseus" paradox.

Regardless of these issues, the Athenians preserved the ship. They believed that Theseus had been an actual, historical figure and the ship gave them a tangible connection to their divine provenance.

Plutarch had proposed a paradox that dealt with identity and change within time. Thomas Hobbes later modified that paradox. It is usually described with two terms of identity, the first being descriptive identity and the second being identity of indiscernibles (otherwise known as Leibniz’s Law). Hobbes presented a complication of the old planks of the ship being saved and put together in the same way to build a new ship. One formula is that the new ship, named the Ariadne, is sent out to sea and over time the crew on board removes the old planks and places newly constructed ones that are identical to the previous ones. While it is sailing in the Aegean Sea, the old planks are dropped off in Piraeus, where a ship is built in the same order that the Ariadne was built with those old planks. Due to Leibniz’s Law, the Aegean ship and the Piraean ship are not the same ship. However, the problem is which one is the same ship as the Ariadne?

One answer is that the Aegean ship is the Ariadne since the planks were renewed and a ship doesn't stop being that ship when the planks are replaced. Another answer is that the Piraean ship is the Ariadne because it was constructed with the same planks the Ariadne was built with. However, they cannot both be the same ship because they aren't numerically identical to each other.

Peter Geach proposed a theory of relative identity where numerical identity does not exist. He created the term of "same F as", "F" being a certain thing. With his logic, it's possible for x and y where x is the same F as y but x is not the same G as y. Based on the theory of relative identity, there are four propositions that one could come up with. The first is since there is no relation of numerical identity, this problem is meaningless. The second is that all three ships are material things. The third is that they are all the same ships but not the same material things, and the last is they are all the same material but not the same ship.