[Z]

The ship of Theseus, also known as Theseus's paradox, is a paradox that raises the question of whether an object which has had all its components replaced remains fundamentally the same object. Plutarch questioned whether the ship would remain the same if it were entirely replaced, piece by piece. Centuries later, the philosopher Thomas Hobbes introduced a further puzzle, wondering: what would happen if the original planks were gathered up after they were replaced, and used to build a second ship. Which ship, if either, is the original Ship of Theseus?

If you replace all of the individual parts of something over time, one by one, is it still the same object? For example, if you replace the glass in a window with new glass; and then later on replace the wooden frame with a new wooden frame - is it still the same window? It's in the same place as the old window and it performs the same function as the old window, but all of the individual parts have changed over time. Does that mean it is different or the same, because the individual parts add up to a whole (i.e. the window)? Is an object an object or is it the sum of all its parts?