In the most daring argument of the Principia, Isaac Newton concluded that the mutual, inverse-square attraction between celestial bodies applies to “all bodies universally.” It follows that any compound body attracts in virtue of all the small parts that compose it. The scope of this universality claim makes it an ideal case study for understanding how researchers in celestial mechanics thought about the logic and limits of evidential support.

In the first part of my talk, I reconstruct how Newton's claim was persistently tested in 200 years of research in physical geodesy and, to a lesser extent, laboratory physics. In the second part of my talk, I articulate an ideal of evidential reasoning that came to explicitly characterise these tests in the nineteenth-century. I dub this ideal “evidential closure” (building on a notion by George E. Smith). Evidential closure requires a theory to be predictively sufficient to account for all contributing causes within an empirically delineated region of its parameter space. I then compare this ideal to alternatives in philosophy of science such as severity, novel predictive success, and puzzle-solving. While not generally preferable in any straightforward sense, it is the only ideal whose pursuit can yield bodies of evidence that are likely to be invariant across subsequent theory change. 

Coffee, tea, cake and fruit will be served before the colloquium @ 2 pm.