Abstract: Inflationary cosmology has been widely accepted for decades. Yet there are persistent debates about inflation which raise central questions in philosophy of science. Skeptics have often expressed doubt regarding whether inflation is "testable" or "falsifiable," due to the flexibility of inflationary models. This is an instance of a general question in philosophy of science: to what extent does phenomenological success support the claim that a theory gets the physics right? How does one answer a skeptical worry, that the theory "fits the data" because it is flexible? My aim in this talk is reframe this debate, drawing on ideas from George Smith’s historical and philosophical assessment of celestial mechanics. Smith answers the skeptic by looking at the role a theory plays in guiding inquiry. Following Newton, astronomers "closed the loop" by starting with an initial description of motions; using discrepancies with observations to identify sub-dominant physical details; incorporating these details into a more refined description; and then starting the process over again. Through this process astronomers discovered hundreds of new details about the solar system, based on assuming the theory of gravity, that could be checked independently. Considering this case helps to characterize one challenge facing theories of the early universe: our lack of clarity about the underlying physics driving inflation has blocked pursuit of a similar process of iterative refinement. I will close by considering several different responses to this challenge.
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