Abstract
Theory-ladenness is the view that observation cannot function in an unbiased way in the testing of theories because observational judgments are affected by the theoretical beliefs of the observer. Its more radical cousin, incommensurability, argues that because there is no theory-neutral language, paradigms, or worldviews, cannot be compared because in different paradigms the meaning of observational terms is different, even when the word used is the same. There are both philosophical and practical components to these problems. I argue, using a procedurally-defined, theory-neutral experiment that paradigms are indeed commensurable. The practical problems of theory ladenness include experimental design, failure to interpret observations correctly, possible experimenter bias, and difficulties in data acquisition. I suggest that there are methods to deal with these problems, although sometimes they cannot be dealt with completely. I believe that the philosophical problems of theory-ladenness have been solved, although the practical problems remain.
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Notes
It is, of course, true that sometimes one might just use a constant-volume-gas thermometer as part of the experiment. In that case no problem arises because the theory of the apparatus and the theory of the phenomenon are distinct. I am discussing an experiment in which only a mercury thermometer is used.
Kuhn offers the following statement on incommensurability: “These examples point to the third and most fundamental aspect of the incommensurability of competing paradigms. In a sense that I am unable to explicate further the proponents of paradigms practice their trades in different worlds…. Equally it is why, before they can hope to communicate fully, one group or the other must experience the conversion that we have been calling a paradigm shift. Just because it is a transition between incommensurables, the transition between competing paradigms cannot be made a step at a time, forced by logic and neutral experience” (Kuhn 1962, 150). “This need to change the meaning of established and familiar concepts is central to the revolutionary impact of Einstein’s theory” (ibid., 102). Feyerabend is more difficult to pin down. At times he states that theories are incommensurable only if they are not interpreted in an “independent observation language” (Feyerabend 1975, 274). Elsewhere he seems to deny the possibility of such a language: “Adopting the point of view of relativity we find that the experiments, which of course will now be described in relativistic terms, are relevant to the theory, we will also find that they support the theory. Adopting classical mechanics we again find that the experiments which are now described in the very different terms of classical physics are relevant, but we also find that they undermine classical mechanics” (ibid., 280).
This has been tested in proton-proton elastic scattering. The angle is less than 90°.
Because, as discussed below, experiment showed that parity was not conserved in the weak interaction the conclusion was that the τ and θ particles were the same particle.
Lee and Yang were awarded the Nobel Prize in physics in 1957 for their suggestion.
The Duhem–Quine problem is that one may protect any hypothesis from refutation by making adjustments elsewhere in one’s knowledge base. For example, one might say that in this case at the same time as the experiment on earth showed parity nonconservation, a similar experiment on Mars showed the opposite effect and that the parity of the universe is still conserved. This would, be difficult, if not impossible to test at this time, although even a local violation of parity conservation would be of interest.
Experimenter bias might also lead to getting results in agreement with previous results, but that is not a theory-ladenness problem.
Notice that experiments designed in the light of Mott’s theory and using its language produced results in disagreement with that theory.
Richard Cox and Bernard Kurrelmeyer confirmed this in private correspondence with the author.
Karaca also presents a very nice summary of recent discussions of theory ladenness.
I distinguish here between exclusion of data and selection of data. Exclusion typically refers to “bad” data, that is data taken when the apparatus is not working properly. Selection appliers to “good” data, obtained when the apparatus is working properly.
One should distinguish between experimental data and an experimental result. They are usually different. What I mean by “analysis procedures” are those processes that transform data into an experimental result. These processes may involve computer analysis and simulation, making cuts on the data, and other procedures.
By valid, I mean that the experimental result has been argued for in the correct way.
For an example see Franklin (2002, Chapter 5). See also the discussion of Rupp’s experiments in the previous section.
BABAR is an elementary particle experiment which includes searches for rare decays, precision measurements, and time-dependent asymmetries in the decays of the B (primarily) and D mesons. The BABAR group consists of more than 500 physicists. The Guidelines were written by the Blind Analysis Task Force and the BABAR Publication Board.
There is an episode in which the experimental data was analyzed and a result presented. The analysis of the same data was later modified to include blind analysis and continued (Franklin 2002, Chapter 6). One could compare the initial results obtained without blind analysis to the later results obtained with such analysis. They differed only slightly. The experiment measured rare decay modes of the D meson. In 1996, unblind analysis, the experimenters reported upper limits for the decays D+ → π+μ+μ− and D+ → π+e+e− of <1.8 × 10−5 and <6.6 × 10−5, respectively. In 1991, blind analysis yielded limits of <1.5 × 10−5 and <5.2 × 10−5 for the same decays.
My colleagues Keith Ulmer and Bill Ford have told me that the BaBar trigger system excluded only small angle Bhabha scattering, the scattering of electrons from positrons.
Each event is quite complex with as many as one hundred or more tracks.
CMS refers to a large, general purpose detector at the Large Hadron Collider. It also refers to the group of more than 2000 physicists who work on the experiments. ATLAS is another such detector and group.
This is the rate of pulse collisions.
This processor farm consists of approximately 1,000 commercial processors.
My colleagues, who are members of the CMS collaboration, inform me that such changes do occur.
Data from events that pass the Level-1 trigger are stored in a buffer. The HLT is then implemented so that a decision can be made as to whether the data should be permanently stored. This must, of course, be done quickly.
A similar table appears for the CMS experiment in Adam et al. (2006).
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Franklin, A. The Theory-Ladenness of Experiment. J Gen Philos Sci 46, 155–166 (2015). https://doi.org/10.1007/s10838-015-9285-9
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DOI: https://doi.org/10.1007/s10838-015-9285-9