Effective theories and infinite idealizations: a challenge for scientific realism
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Effective theories and infinite idealizations: a challenge for scientific realism Sébastien Rivat1 Received: 6 September 2019 / Accepted: 31 August 2020 © The Author(s) 2020
Abstract Williams and J. Fraser have recently argued that effective field theory methods enable scientific realists to make more reliable ontological commitments in quantum field theory (QFT) than those commonly made. In this paper, I show that the interpretative relevance of these methods extends beyond the specific context of QFT by identifying common structural features shared by effective theories across physics. In particular, I argue that effective theories are best characterized by the fact that they contain intrinsic empirical limitations, and I extract from their structure one central interpretative constraint for making more reliable ontological commitments in different subfields of physics. While this is in principle good news, this constraint still raises a challenge for scientific realists in some contexts, and I bring the point home by focusing on Williams’s and J. Fraser’s defense of selective realism in QFT. Keywords Effective theories · Effective field theories · Renormalization group · Scientific realism · Selective realism · Infinite idealizations
1 Introduction There is a deeply entrenched strategy in philosophy of physics about how to interpret our best theories in realist terms. Philosophers usually start by pretending that the theory at stake is complete, true and final, even if it is known not to be true in all respects. Then, they eliminate its redundant parts by implementing sophisticated constraints on its structure. And eventually, they draw from the resulting theory some putatively complete picture of the world. The goal, ultimately, is to identify a definite set of
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Sébastien Rivat [email protected] Max Planck Institute for the History of Science, Boltzmannstraße 22, 14195 Berlin, Germany
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unobservable entities or structures, whether they are fundamental or not, and thereby lay the ground for explaining the success of the theory in realist terms.1 As it turns out, this strategy somewhat falls apart in the case of our most fundamental and empirically successful theories. We do not yet know whether realistic quantum field theories (QFTs) can be consistently defined across all scales and therefore whether we can even consistently speculate about the possible worlds in which these theories are exactly true. Wallace (2006, esp. Sect. 3.3; 2011), Williams (2019b), and J. Fraser (2018, 2020) have proposed a more modest and cautious strategy in response, which is also better suited to the limited success of current and past theories. They enjoin philosophers to identify the ontological commitments necessary to explain the success of our best QFTs in the limited regimes where they are known to be reliable and not in the regimes where they are likely to break down. The crucial part of Wallace, Williams and J. Fraser’s proposal resides in the set of techniques they employ to implement this new
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