According to the Greek myth, retold by Plutarch, the ship on which Theseus returned from Crete to Athens was carefully kept by the Athenians until the era of Demetrius of Phaler, and was annually sent with a sacred embassy to Delos. When repairing it, the boards were gradually replaced, until a dispute arose among the philosophers, is it still the same ship, or is it another, new? In addition, the question arises: if a second ship is built from old planks, which one will be real?
Theseus' ship is a paradox, which can be formulated as follows: "If all the constituent parts of the original object were replaced, does the object remain the same object?"
The solution to the paradox lies in the vagueness of the concept of “the same”. Depending on how you ask it, there will be different answers. One can only discuss which definitions correspond to one or another idea of identity.
Several solutions to this paradox have been proposed. According to the philosophical school of Aristotle, there are several reasons describing the object: form, material and essence of a thing (which, according to Aristotle's teachings, is the most important characteristic). Based on this, the ship remained the same, since its essence has not changed, only the worn out material has changed.
In the next decision, it was proposed to give the argument "the same" quantitative and qualitative characteristics. In this case, after changing the boards, Theseus' ship will be quantitatively the same, but qualitatively - a different ship.
Recently, to solve the Theseus paradox, it was proposed to use a 4-dimensional interpretation, in which a 3-dimensional ship also has an extent in 4 dimensions-time. The resulting 4-dimensional ship is quantitatively identical with itself throughout the time series. But individual "time slices" can be qualitatively different from each other.