Recent studies of the English modals focused on may and can seem to converge on notions of what is imposed from outside (another's will, or some other external power) and what is possessed by or vested in a person, thing, or situation. The first includes what is granted as possible: permissions and predictions, the latter including epistemics, which are past or present facts yet to be verified. The second adds the dimension of potentiality, or ability in the broadest sense. I define the opposition as extrinsic possibility versus intrinsic potentiality, or simply possibility versus potentiality. © 1989.
Bolinger, D. (1989). Extrinsic possibility and intrinsic potentiality: 7 on may and can + 1. Journal of Pragmatics, 13(1), 1–23. https://doi.org/10.1016/0378-2166(89)90107-0