The Unanchored Ship Of Theseus

Humanity, Kai knows, is a concept. It has nothing to do with the fact that his body is now wires versus neurons, and whether his skin is flesh and blood or if it, well . . . Isn't. He tells himself these things like a mantra, an unanswered prayer every time they lock him away again and leave him to his own devices. It's not like he has anything better to do in the empty cell; there are no windows with which to see the stars beyond, no bed to sleep upon, not that the latter is something he needs anymore. He doesn't even have a light to see by, his automatic night vision program kicking in when the door shuts and takes the last sliver of it away.

The only thing they've left him with is himself, and by this point Kai isn't even really sure who that is anymore.