An objection asks whether the possibility of disagreement between two hypothetical wills requires actual disagreement. Perhaps both always choose the same outcome.
Possibility and actual occurrence are distinct. A possible event may never happen; conversely, the mere possibility of an event does not license the claim that it has happened.
A response might try to show that independent sovereignty cannot rule out conflict by an intrinsic necessity. Unless that additional step is established, “two wills exist, therefore they already disagree” goes beyond the premise. This is one major point on which the proof must be examined.