In principle our best physics tells us that determinism is just false as a metaphysics.
As said above and elsewhere, MWI is perfectly deterministic. It’s just that there is no single fact of the matter as to which outcome you will observe from within it, because there’s not just one time-descendant of you.
Thats a fair point, but I don’t think it is quite that easy. On one formulation a deterministic system is a system whose end conditions are set by the rules of the system and the starting conditions. Under this definition, MWI is deterministic. But often what we mean by determinism is that it is not the case that the world could have been otherwise. For one extension of ‘world’ that is true. But for another extension, the world not only could have been otherwise. It is otherwise. There are also a lot of confusions about our use of indexicals here: what we’re referring to with “I”, “You”, “This”, “That” My” etc. Determinism usually implies that ever true statement (including true statements with indexicals) is necessarily true. But it isn’t obvious to me that many worlds gives us that. Also, a common thought experiment to glean people’s intuitions about determinism is basically to say that we live in a universe where a super computer that can exactly predict the future is possible. MWI doesn’t allow for that.
Perhaps we shouldn’t try to fit our square-pegged physics into the round holes of traditional philosophical concepts. But I take your point.
Why would determinism have anything to say about indexicals? There aren’t any Turing-complete models that forbid indexical uncertainty; you can always copy a program and put the copies in different environments. So I don’t see what use such a concept of “determinism” would have.
Thinking about this it isn’t a concern about indexicals but a concern about reference in general. When we refer to an object we’re not referring to it’s extension throughout all Everett branches but we’re also referring to an object extended in time. So take a sentence like “The table moved from the center of the room to the corner.” If determinism is true we usually think that all sentences like this are necessary truths and sentences like “The table could have stayed in the center” are false. But I’m not sure what the right way to evaluate these sentences is given MWI.
IAWYC except, of course, for this:
As said above and elsewhere, MWI is perfectly deterministic. It’s just that there is no single fact of the matter as to which outcome you will observe from within it, because there’s not just one time-descendant of you.
Thats a fair point, but I don’t think it is quite that easy. On one formulation a deterministic system is a system whose end conditions are set by the rules of the system and the starting conditions. Under this definition, MWI is deterministic. But often what we mean by determinism is that it is not the case that the world could have been otherwise. For one extension of ‘world’ that is true. But for another extension, the world not only could have been otherwise. It is otherwise. There are also a lot of confusions about our use of indexicals here: what we’re referring to with “I”, “You”, “This”, “That” My” etc. Determinism usually implies that ever true statement (including true statements with indexicals) is necessarily true. But it isn’t obvious to me that many worlds gives us that. Also, a common thought experiment to glean people’s intuitions about determinism is basically to say that we live in a universe where a super computer that can exactly predict the future is possible. MWI doesn’t allow for that.
Perhaps we shouldn’t try to fit our square-pegged physics into the round holes of traditional philosophical concepts. But I take your point.
Why would determinism have anything to say about indexicals? There aren’t any Turing-complete models that forbid indexical uncertainty; you can always copy a program and put the copies in different environments. So I don’t see what use such a concept of “determinism” would have.
Thinking about this it isn’t a concern about indexicals but a concern about reference in general. When we refer to an object we’re not referring to it’s extension throughout all Everett branches but we’re also referring to an object extended in time. So take a sentence like “The table moved from the center of the room to the corner.” If determinism is true we usually think that all sentences like this are necessary truths and sentences like “The table could have stayed in the center” are false. But I’m not sure what the right way to evaluate these sentences is given MWI.
Voted down because my writing is confusing or because I said something stupid?