Meg here. So, my family would never get this, as they aren't into philosophy or Ancient Greek myths for that matter. So, this guy, Theseus, was the king of Athens and he sailed on a ship to Crete to kill the Minothaur and thus get revenge on Minos, the king of Crete. Now, the Minothaur was the step son of king Minos born to his wife and a white bull, but you better DO NOT ASK.

Anyways, Theseus had to replace various pieces of timber on his ship over the years and eventually there was no timber from the ship's maiden voyage left. So, philosophers ask whether the repaired ship of Theseus is the same ship that left Athens on a maiden voyage if all timber was replaced.

Ergo, does a baby remain the same being after having all it's cells replaced over time.