If I had a ship and replaced one of its planks is it still the same ship? what if I replaced two planks? what If I replaced half of the planks or all the planks is it still the same ship? What if over time I replaced all the old planks over time but I saved all the old planks and but I kept all the old planks and then put the planks back together to make a second ship. Which of the two ships is the original ship the one that was first built or the one that is made up of the original parts?