ho.ho.cho said:
I keep hearing this. What is amusing about it is
three-fold:
1. The arbitrary distinction between science and philosophy. Most of
Newton's written works dealt with theology. Einstein never erected any
kind of firewall between his 'scientific' and 'religious' ideas, which
meant he could make objections like "God does not play dice". The best
minds in physics routinely mix what might be called 'scientific' and
'religious' lines of thought -- not when it comes to scientific proof or
demonstration, but always at the level of personal imagination and
thought. The idea therefore that there is 'mere philosophy' seems more
something people on the lower rungs of the physics ladder repeat in a
natural tendency to assert the importance of their own field.
There is no arbitrary distinction between (natural) science and philosophy. In fact, there is a precise cut between these fields. Whether a question falls in the former or the latter field can ultimately be decided by asking: "Can the question be answered by means of experiment or not?"
That doesn't mean that there can't be people who do both physics and philosophy, but I'm sure that at least Einstein was very aware of that fact that his statement "God does not play dice" is a purely philosophical one. That's why he suggested the EPR experiment in the first place: He hoped that the question could be settled in his favour. But actually there has not been a single experiment in the history of physics that could evade the counter-intuitive consequences that come with quantum mechanics and I'm pretty confident that even Einstein would have had to accept this if he had managed to survive until today.
By the way: I find your statement about "people on the lower rungs of the physics ladder" very arrogant and i also wouldn't count myself to to them. In fact, my own research covers foundational questions of quantum physics.
ho.ho.cho said:
2. When it comes to questions like, for example,
the 'completeness' of a given theory -- some of the best minds in physics
dealt with this question on both sides of the debate. To therefore declare
that the question of, in this case, the completeness of QM is a
non-scientific one or 'mere philosophy' demonstrates an ignorance of what
science is. Scientific demonstration always takes place within a broader
conceptual and mental context. While the rules of demonstration and
argument must always remain rigorous, the generation of scientific
knowledge always takes place in a broader, less rigorous context of free
thinking. I'll just note in passing that the EPR paper seems to reflect
exactly this. The broader context dealt with the issue of completeness.
The narrower context dealt with the so-called EPR paradox. According to
Wikipedia:
So at the heart of the EPR paper was a thought-experiment involving two
entangled particles. This was the experimental side of the argument. The
other side dealt with the 'completeness' of theories using a narrow
definition. It was no less scientific just because it touched on matters
not strictly undertaken within experimentation. It informed the creation
of the thought-experiment.
Philosophy is also a science, but it is not a natural science. I think the misconception about "what science is" is on your side. Your very own definition of "completeness" was:
ho.ho.cho said:
"In a complete theory there is an element corresponding to each element of reality."
This definition however, is too vague to be useful, since it includes the word "reality", which itself is vague, unless you state more precisely what it is supposed to mean.
My basic point is that there is absolutely no way to state what "reality" is in the scope of physics, because physics always needs to stay agnostic with respect to this question. Physics is only concerned with the description of observable phenomena, but it doesn't include any assertions about the "true nature of the world". This basic fact has been known since the 30s and is actually a major cornerstone of all natural sciences and everyone who legitimately claims to be a physicist must understand this basic fact. So if you don't understand it, you should definitely read up on it. A good start might be this Wikipedia article:
http://en.wikipedia.org/wiki/Falsifiability
Having understood this, you must agree that assertions about the "true nature of the world", which includes certain preconceptions about "reality", fall out of the scope of natural science and thus belong to philosophy.
I want to emphasize again that this doesn't prevent anybody from being both a physicist and a philosopher, but the distinction between these fields always has to be clear and should not be mixed up. I'm also not saying that these fields musn't influence each other. I just want to distinguish questions which can be answered by methods of natural science and questions that involve personal prejudice about what the world is like.
To summarize this again: The concept of "completeness" of a theory is always based on personal preconceptions that can't be falsified and is thus not a legitimate criterion in the field of natural sciences. Two theories that make exactly the same predictions (like Bohm and Copenhagen) can't be distinguished from the point of physics. They can however be distinguished from a philosophical viewpoint that includes additional input that can't be gained by experiments and thus doesn't add anything to the knowledge of the laws of physics.
ho.ho.cho said:
3. The above is already a philosophical interpretation, a philosophical conclusion derived from a certain reading of the EPR/QM dispute. There is nothing in the EPR paper, for example, that has to do with the ultimate meaning of reality. So where does the commenter above get this?
I was just referring to your own definition:
ho.ho.cho said:
"In a complete theory there is an element corresponding to each element of reality."
As i already argued, this definition is not at all narrow enough (as you suggested) to be regarded as a useful criterion for natural science.
ho.ho.cho said:
I would say that all leading physicists are concerned with what 'reality' is to the extent they are concerned with the truth of what they are saying.
You have a misconception about what physics is. Physics is never concerned with the "truth" of a theory. All physicists have accepted the fact, that a theory can never decided to be true. All we have is falsifiability. Thus a physicists is also not concerned with "what reality is", but how to describe every observable phenomenon. More just can't be accomplished with the methods of physics. Everything beyond the pure description of observable phenomena must be regarded as philosophy. I don't want to disdain philosophy. I just want you to accept that it doesn't add anything to our knowledge, because it is only concerned with "what-if" questions like "what if Bohmian mechanics were true". It doesn't assert that Bohmian mechanics is true. It only asks "what would the world be like if it were true" without making a definite descision of whether it is true or not.
ho.ho.cho said:
Even if they decide that the reality in question cannot be determined because for example the collapse of the wave function is an objectively real fact; or, if on the other hand, they think there is no objective collapse, but the true situation is unknowable. The point here is, though, that these differences in 'mere philosophy' drive the direction of research. Experiments are devised and performed in order to test these differing perspectives in 'mere philosophy'.
Now we are discussing something entirely different. Whereas physics can't decide whether the Copenhangen or the Bohm interpretation of quantum mechanics is better, this is different with the theories you suggest now. For example, objective collapse theories usually involve modifications of the Schrödinger equation, which can be tested experimentally and are thus legitimate theories of physics that definitely deserve further investigation and not just mere philosophy. This also applies to most other directions of research in quantum physics foundations. However Bohmian mechanics does not count to these directions of research.