Ship of Theseus

First recorded by Plutarch in his Life of Theseus (first century CE), where Athenians debated whether the legendary hero's ship — its planks replaced one by one as they decayed — remained the same vessel. In the 17th century, Thomas Hobbes sharpened the paradox by imagining someone rebuilding a second ship from all the discarded planks, forcing the question of which vessel was the "original."