ABSTRACT
Fruitful as this kind of approach has been, though, such internal debates often seem to flounder on two related questions. The first is the question of what makes something a second person this or that – how do we distinguish between stipulation and substance? Call this the ‘existential question’. The second is the question of why it matters whether there are such things, what kind of difference does one answer or another to the existential question make? Call this the ‘significance question’. Of course, how one answers the latter depends, in part, on answers to the existential question, which in turn can, and arguably should, be influenced by the significance question, and there is danger of reaching a point where wheels begin to spin in a vacuum.
