"what if the ship of theseus was sentient" is not a question I was prepared to grapple with

The image is from a Thomas the Tank Engine picture book. A mechanic is putting a new smokestack on Thomas with a crane. Thomas looks up with an expression that can be read as surprise or wonder. Underneath the image is the following text: Thomas didn't enjoy his time at the Works. "It's nice to feel mended again," he said afterwards, "but they took so many of my old parts away and put new ones in, that I'm not sure whether I'm really me or another engine."