On 10/28/2022 6:43 PM, Bruce Kellett wrote:
On Sat, Oct 29, 2022 at 11:51 AM Brent Meeker <meekerbr...@gmail.com> wrote:On 10/28/2022 5:43 PM, Bruce Kellett wrote:On Sat, Oct 29, 2022 at 11:37 AM Brent Meeker <meekerbr...@gmail.com> wrote: On 10/28/2022 5:28 PM, Bruce Kellett wrote:On Sat, Oct 29, 2022 at 10:54 AM Brent Meeker <meekerbr...@gmail.com> wrote: On 10/28/2022 4:38 PM, Bruce Kellett wrote:On Sat, Oct 29, 2022 at 10:27 AM Brent Meeker <meekerbr...@gmail.com> wrote: On 10/28/2022 3:06 PM, Bruce Kellett wrote:Simply saying that QM as traditionally formulated considers measurement as a special process that os irreversible, doesn't cut it, because measurement is then not treated in terms of the fundamental dynamics of the theory, it is put in in an ad hoc way. Lots of things are put into physics in an ad hoc way. The Born rule is a prime example -- it is just imposed on the quantum wave function in an ad hoc way -- it cannot be derived from the fundamental theory.But by Gleason's theorem it's the only consistent way to put a probability measure on Hilbert space. Who said we need a probability measure?Because we observe that the same initial condition results in different later conditions, but with predictable probability distributions. That is what is known as an ad hoc adjustment of the theory -- anything that is required for the theory to agree with observation. Let's face it, all of physics is ad hoc!That is as ad hoc as anything else; besides, unitary QM does not allow for a probabilistic interpretation.Not if you insist that all evolution is unitary, but that's why Born added the projection postulate to connect the unitary evolution to observation. But Saibal and his ilk are insisting that all physics is unitary. That is why the addition of probability (and the Born Rule) is just an ad hoc adjustment so that their theory agrees with observation. Gleason's theorem does not change this fact.It's not "ad hoc" when it's part of a theory that applies to everything. That is just an arbitrary stipulation.ad hoc ăd hŏk′, hōk′ adverb 1. For the specific purpose, case, or situation at hand and for no other. 2. On the spur of the moment. 3. For a particular purpose.For the particular purpose of relating the theory to observation, it is certainly ad hoc.
That's pretty damned broad reading of "particular".
Look, "ad hoc" is frequently bandied about as a fatal flaw in any theory. Just as Putin waves about the nuclear threat: this is just to intimidate the opposition, it doesn't mean anything more. Any theory has ad hoc elements, or else it would not be of any value in explaining our experience. There is always a theoretical part, and then a collection of elements that serve to relate the theory to observation. Everything is ultimately ad hoc, because it is for the particular purpose of explaining observation.
I think you've stretched it's meaning beyond recognition. If every theory that is devised to match experiment is ad hoc then indeed all science is ad hoc...and the better for it. But there is real ad hockery that is deserving of criticism.
The real question on the table is what would you take to be not ad hoc; what would be better than "... measurement is then not treated in terms of the fundamental dynamics of the theory." Do you see MWI doing this?
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