Abstract

In her 1996 book, Error and the Growth of Experimental Knowledge, Deborah Mayo argues that use- (or heuristic) novelty is not a criterion we need to consider in assessing the evidential value of observations. Using the notion of a “severe” test, Mayo claims that such novelty is valuable only when it leads to severity, and never otherwise. To illustrate her view, she examines the historical case involving the famous 1919 British eclipse expeditions that generated observations supporting Einstein's theory of gravitation over Newton's. My plan here is to defend use-novelty as a valuable methodological principle. I begin by exposing a weakness in Mayo's criticism of use-novelty. Remedying this weakness re-establishes the worth of use-novelty under specific conditions; in particular, heuristically novel data are to be preferred, as I will say, “prima facie”. Armed with this revised version of use-novelty, I re-examine the history of the eclipse experiments and offer an interpretation of this episode that to an extent—and contrary to Mayo—restores the mildly heretical, Earman/Glymour evaluation of this episode offered in their (1980). I conclude by responding to criticism of my assessment of Mayo's work.