That's true, but that doesn't mean if you build an identical ship next to mine that your ship is "the same ship." Further, I'll be pissed if the one I'm on sin

That's true, but that doesn't mean if you build an identical ship next to mine that your ship is "the same ship." Further, I'll be pissed if the one I'm on sinks. The identical one sailing off into the distance is cold comfort to me.