Are you saying that this A-theory predicts that there is a preferred foliation?
Not to speak for pragmatist, but, yes, that is my understanding. But, importantly, the foliation isn’t just preferred by some distinguishing physical characteristic (the way a preferred reference frame would be, for example). Rather, the foliation is preferred in a more ontologically fundamental sense: When one leaf exists, no other leaves of the foliation exist at all, nor do the parts of spacetime that they would “foliate”. For the presentist/A-theorist, at this moment, a completely exhaustive ontology of the world contains nothing that is not in the present leaf.
By that logic, wouldn’t B-theory predict that no foliation is possible at all? Or that all foliations are equal, whether they are timelike, null or spacelike? If so, the B-theory has been clearly falsified (if you can ever falsify anything in philosophy of physics).
The B-theory allows foliations to be different from one another in physically real ways. The B-theory doesn’t allow that leaves of one special foliation “pass into and out of existence”, which is what the presentist/A-theoretic approach requires.
(That is my understanding of what a presentist would say, anyway. But, as I said, I can’t really make sense of presentism, so I might not be portraying the view accurately.)
Not to speak for pragmatist, but, yes, that is my understanding. But, importantly, the foliation isn’t just preferred by some distinguishing physical characteristic (the way a preferred reference frame would be, for example). Rather, the foliation is preferred in a more ontologically fundamental sense: When one leaf exists, no other leaves of the foliation exist at all, nor do the parts of spacetime that they would “foliate”. For the presentist/A-theorist, at this moment, a completely exhaustive ontology of the world contains nothing that is not in the present leaf.
The B-theory allows foliations to be different from one another in physically real ways. The B-theory doesn’t allow that leaves of one special foliation “pass into and out of existence”, which is what the presentist/A-theoretic approach requires.
(That is my understanding of what a presentist would say, anyway. But, as I said, I can’t really make sense of presentism, so I might not be portraying the view accurately.)