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Old 22nd August 2011, 04:18 AM   #107
Dave Rogers
Bandaged ice that stampedes inexpensively through a scribbled morning waving necessary ankles
 
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Originally Posted by stevea View Post
That statement is not supportable. Just because we haven't demonstrated any improved basis for selection among hypotheses does not mean that such a selection criteria does not exist. It also ignores my objection that Occam's Razor(OR) criteria is not easy to define in practice.
I'm not arguing that there is no possible criterion superior to OR, simply that we have none at present. If someone suggests a better one, then it's worh considering; until then, we're simply discussing meaningless hypotheticals.

Originally Posted by stevea View Post
Yes there are an infinite number, but I disagree that we can't maintain them all. Isn't this exactly what we do when we keep an open mind where evidence hasn't accrued ? Since this method avoids selection of a single likely-falsifiable hypothesis then it is not a waste of effort - it's potentially a great savings.
There's no need to reject unfalsified theories of greater complexity or requiring more unverified assumptions as possible future hypotheses, and nobody is suggesting that there should be. It's simply more economical of effort to choose a single current working hypothesis. If it isn't obvious why it's less effort to base our predictions on a single theory, rather than to have to perform them several times based on different theories that are known in advance to present the same result, it's a bit difficult to explain.

Originally Posted by stevea View Post
No, it's not an infinite task. It's just a matter of directly representing our lack of knowledge within the scientific model rather than making a presumptive guess about the OR hypothesis.
Occam's Razor explicitly represents that lack of knowledge, by virtue of being an arbitrary but well-defined means of choosing the theory of current usefulness. The fact that we employ it in the first place is a recognition that there are multiple theories of equal merit.

Originally Posted by stevea View Post
You are viewing my suggestion incorrectly. I did not say that we should should tentatively accept each individual hypothesis that matches current knowledge. I suggested that we tentatively accept the entire class as a whole. That we embrace and quantify the lack of knowledge. So there is no "costly blunder" coming down the road.
If we accept the entire class as a whole, then we take on an infinite task. If we select among the class in order to define a finite task, then we risk a "costly blunder" if the selection criterion excludes all theories that are required to explain new data. So, given that we risk a "costly blunder" in order to be able to make any predictions at all, we might as well do so in as efficient a fashion, by selecting a single workable theory.

Originally Posted by stevea View Post
Occam's Razor does select a single simple hypothesis among the set, and therefore it typically selects a falsifiable (wrong) hypothesis.
"Falisifable" =/= "Wrong". And any selected hypothesis or group of hypotheses must be falsifiable in order to be useful.

Originally Posted by stevea View Post
Any explanation based on this may be wrong as a result. You are assuming that an arbitrary simple guess at a hypothesis has more explanatory power then considering the full set of possibilities and the factual limitations of the observations.
No, I'm arguing that it is a practical impossibility to consider the infinite set of possible theories, therefore an arbitrary choice among them must be made in order for science to produce any useful results. The only argument to be had is over the set of criteria used for this arbitrary choice, and at present OR is the best one we know.

Originally Posted by stevea View Post
My point is not to present some new scientific method full-blown, and it's not reasonable for you to (repeatedly now) demand that.
Yes, in fact, it is perfectly reasonable. You're suggesting we abandon the foundation of the science and technology that makes our entire civilisation possible. It's perfectly reasonable to ask what you propose to use instead. And, if you haven't specific to offer, it's equally reasonable to ask you to get back to me when you have.

Originally Posted by stevea View Post
I am primarily arguing that the single hypothesis, Occam's Razor(OR) selection criteria is a very weak point in the 'standard model' and that there may well be better ways to represent observational knowledge.

What I am suggesting is that in addition to accumulating the simplest OR hypothesis that we also incorporate the limitations of the observations and conclusions directly in the model. We want the error bounds and we want the limited experimental conditions reflected in the model.
What makes you think we don't do that already? It's commonplace in science to recognise that the theories we have are valid only for the observational range over which they have been verified, and that observations outside that range may require new theories to describe them. Beyond that, how exactly are we supposed to incorporate knowledge we don't have yet into corrent theories?


Originally Posted by stevea View Post
Perhaps you didn't recognize the language, but OR, and the parsimony principle is said to select the hypothesis with the least number of presuppositions. So yes it matters greatly wrt to the the 'scientific method' which hypothesis has the least presuppositions, since that determines which hypothesis is selected for inclusion.



Aside: So Lorentz eqn has no benefit whatsoever over the Newtonian model ? That's not a statement I can support.
Please don't accuse me of making strawman arguments in the course of making your own. My point is that it's irrelevant to your specific example which is a greater presupposition, and that the Lorentz equation has no benefit over the Newtonian model for predictions in a regime where the differences are negligible. As, indeed, is still the case; most mechanics problems are still solved using the Newtonian model, because the insignificant corrections applied by using the Lorentz model confer no benefit whatsoever.

Originally Posted by stevea View Post
You are making another strawman argument against my suggestions. I never said that we should carry out calculations on the entire infinite class of hypotheses.
You can't have it both ways. Either we use an infinite set of hypotheses, which is a practical impossibility, or we select a subset of hypotheses on purely arbitrary criteria. If the latter, then OR is the best we know.

Originally Posted by stevea View Post
You seem obsessed with the amount of computation involved, or with the theoretical complexity involved in considering a class of hypotheses but that is not really a great issue in practice.
If you honestly think that it's no more difficult to simultaneously maintain a large set of models than to focus on a single one, then I wonder what reality you're inhabiting. It's a very serious issue if we're required to carry out every theroetical analysis several times over instead of just once.

Originally Posted by stevea View Post
Newton might study kinetic energy vs velocity & mass under a restricted range of velocities and mass and with some limited accuracy, and after some polynomial fitting might still conclude that KE = (1/2)*m*v^2 ,but ... A: under the range of the experiment, B: within some calculated error bounds, and C: other higher velocity terms are zero to within the accuracy of the experimental method. This form of hypothesis would incorporate the limitations of the hypothesis within the model. This form of conclusion does not contradict the relativistic calculation of KE. All this does is explicitly include the limitations in the model.
Fine, but that's implicitly understood by every scientist in every discipline. What exactly is it that you want us to do differently? If we have to "consider a class of hypothesis", do we just have to add disclaimers saying "This model may turn out to be wrong in the light of future discoveries"? If not, what? Other than maintain multiple parallel theories - a monstrous waste of time, given that all of them may well turn out to be incorrect - how are we supposed to do things, if not the way we do them now?

It's easy enough to make handwaving complaints that science doesn't live up to your own personal standards, but extremely difficult to make practical suggestions as to how it should. You're not offering any other than vague suggestions that we should somehow consider multiple hypotheses without actually having to do the extra work required to consider multiple hypotheses. Until you have something more concrete and less self-contradictory, I think we'll stick with a method that works well enough.

Dave
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