Full Idea
Though there is a way things logically could be according to which I am a credit card account, there is no way things metaphysically might be according to which I am a credit card account. This illustrates the restricted nature of metaphysical modality.
Gist of Idea
Bizarre identities are logically but not metaphysically possible, so metaphysical modality is restricted
Source
Nathan Salmon (The Logic of What Might Have Been [1989], III)
Book Reference
Salmon,Nathan: 'Metaphysics, Mathematics and Meaning' [OUP 2005], p.136
A Reaction
His drift is that metaphyical modality is restricted, but expressing it in S5 modal logic (where all worlds see one another) makes it unrestricted, so S5 logic is wrong for metaphysics. I'm impressed by his arguments.
Related Idea
Idea 14681 Logical necessity is free of constraints, and may accommodate all of S5 logic [Salmon,N]