The possibility argument

Suppose it is true that if the soul is possibly immaterial it is necessarily so.

Still, there seems to be an equivocation between the soul being conceivably immaterial and it being possibly so.

There is a difference between epistemic and objective possibility.

The former may reflect crucial ignorance that, if remedied, would both preclude it and exclude the latter.

If the case may be such then to invoke the former to prove the latter is begging the question.

But it may be replied that the alleged difference pertains to a posteriori possibility - physical, psychological, or technical possibility, say, - of the bounds of which one may well be ignorant.

But metaphysical possibility, a priori possibility, which is what is at issue here?

Really?