

An argument for impossibilism
(1) Possibilism is true only if some metaphysically possible non-godlike agent has the power of self-creation.
(2) Necessarily: to the extent that the "new" self one acquires rationally follows from the principles of choice (values, preferences, etc.) of one's previous self, there is no creation; one's "new" self is prefigured in the previous one.
(3) Necessarily: to the extent that the new self one acquires doesn't rationally follow from the principles of choice (preferences, values, etc.) of one's previous self, one is not a source of this new self.
(4) If (2) and (3), no metaphysically possible non-godlike agent has the power of self-creation.
(5) No metaphysically possible non-godlike agent has the power of self-creation. (2-4)
(6) Impossibilism is true. (1,5)