What does relativism have to do with anything? It wasn't mentioned by me or previously in this post. Maybe there is a problem with terms here [1], to me positivism does _not_ posit that there is an underlying truth that we get closer to.
Of course if theories make distinct predictions deciding between them is a matter of physics and not philosophy. But it is a fact that the philosophical idea that all knowledge derives purely from observable phenomena and does not need to describe an underlying reaity that is being measured is cited by Heisenberg as a starting point of his investigation of QM that led to matrix mechanics.
Of course if theories make distinct predictions deciding between them is a matter of physics and not philosophy. But it is a fact that the philosophical idea that all knowledge derives purely from observable phenomena and does not need to describe an underlying reaity that is being measured is cited by Heisenberg as a starting point of his investigation of QM that led to matrix mechanics.
[1] Indeed the SEP says there are no clear distinctions but merely overlaping schools of thought: https://plato.stanford.edu/entries/logical-empiricism/