In my post Monday I discussed the three mathematically equivalent ways of framing mechanics. What was so interesting (to me at least) was that these three different formulations all seemed to have different meanings. At least in terms of the entities mechanics was framed in terms of. Now as I said, this isn't a problem for some people. What I wish to do is explain why it is for some and then touch on why it isn't for others. Obviously everyone is going to have different intuitions in this regard. I'll fully admit that mine were, as an undergraduate, all about assuming that the entities we discuss in science correspond in some way to entities in the real world. This might be termed simple scientific realism.
Probably the best formulation of the view I held can be found in this statement by Wilfrid Sellars:
...to have good reason for holding a theory is ipso factor to have good reason for holding that the entities postulated by the theory exits. (Perception and Reality, 97)
Now when we consider this statement of realism with the three formulations of mechanics we quickly see the problem. There are three different, yet ultimately incompatible, sets of entities mechanics is framed in terms of. Now I'm sure some will jump up and contest this, arguing for momentum, potential and kinetic energy, mass and so forth. But if we take Sellars to be saying that is the ultimate entities the theory is framed in terms of that we have epistemic justification to believe exist, then we see the problem. We can have multiple mathematically equivalent theories in this sense of theory. This is often called having the theory underdetermined.
An other way of looking at the issue is to talk about empirical adequacy. In this view the acceptance of a theory isn't to necessarily accept the entities postulated by the theory. It is just to accept that the theory accounts for the kinds of phenomena we encounter or would potentially encounter. So, for instance, we might be unable to say if mechanics really is about minimize the difference in kinds of energy or is due to forces between masses. We can just say that whatever's going on underneath, the theory explains the kinds of phenomena we encounter.
This, roughly is the distinction in science between realism and anti-realism. Now there are many more subtle positions in both camps. For instance empirical adequacy can be taken in many ways. It might be taken in terms of explaining "sense-data" our mind encounters or it might just entail the kinds of quantitative measurements scientists make. Likewise realism can be taken in the strong form as a claim about the entities a theory is made in terms of. Or it might just be taken as a claim that a description of reality is accurate without necessarily embracing strong metaphysical claims.
Now my own position is to be roughly in the realist camp. If only because I think science isn't just about making adequate descriptions without worrying about the reference of these descriptions. That is science isn't just about being useful but is ultimately about reality itself. However I'd be the first to admit that in some ways this is a difficult position to take.
Beyond my examples from mechanics consider the electron. Now I suspect many people would consider the statement "electrons exist" to be true. But what do we mean by an electron? That is, what is this entity? Is it something real and independent? Or is it more a description of a phenomena. We all learned in Junior High to picture electrons as masses orbiting a nucleus or flowing down electrical wire. However by college we'd learned that this wasn't quite right. Further, in quantum mechanics, pinning down the electron became much more difficult, especially when considering the flow of electricity in a wire.
Then there are things called virtual particles. These are theoretical entities that arise in quantum mechanics when we formulate it in terms of the Lagrangian. We can talk about virtual particles "carrying" the forces between particles. So when two electrons repel each other this theory talks about virtual particles moving between the two. But are they "real" or are they just a mathematical artifact? It would be hard to say at the best of times, much as with the problem of the Lagrangian and Newtonian formulations of classical physics. But now we have the problem that they can't be measured and are thus inherently virtual. So are they existing or not? We can't say.
Needless to say the more one gets into theoretical physics the more difficult a naive realism becomes. That's not to say one can't still keep to the realist position. But one has to be careful.
However different problems pop up for the anti-realist. For one we have the classic problem of the fact/value distinction. That is how do we characterize empirical adequacy if the phenomena (what we measure or experience) is itself partly determined by theory. Consider once again the electron. Is the electron of quantum theory, with the different way of thinking about it, the same electron from the 19th century? For the realist this is an easy answer. Yes. We just had some erroneous ideas about it. For the anti-realist it's a more difficult answer since our ideas of it are so wrapped up with what it is to accept a theory. That is my experience of measuring something about an electron are wrapped up in my understanding of what it is to be an electron.
Now some might avoid this and say, so long as we just worry about measurements (the numbers) this doesn't matter. And perhaps that's the easiest and safest approach. And some might say that "sense-data" is raw and not theory ladden. However there are large disputes within the philosophy of science about whether phenomena and even quantitative data can be separated from theory easily.
If they can't there is the problem of the incommesurability of theory. This is basically the idea that when there is a significant change in ones foundational theories (as say our theories about the electron) that we can't really say earlier people were talking about the same things at all.
Is this a problem? Probably not, although it would suggest the way history of science is sometimes taught is misleading. And overall I'd say that "empirical adequacy" is probably the safest position to take. However, as I said, it's not the position I take.
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