 Radder (1996, 2003, 2006, 2009, 2012) distinguishes three types of reproducibility. One is the reproducibility of what Radder calls an experiment’s material realization. Using one of Radder’s own examples as an illustration, two people may carry out the same actions to measure the mass of an object. Despite doing the same actions, person A regards themselves as measuring the object’s Newtonian mass while person B regards themselves as measuring the object’s Einsteinian mass. Here, then, the actions or material realization of the experimental procedure can be reproduced, but the theoretical descriptions of their significance differ. Radder, however, does not specify what is required for one material realisation to be a reproduction of another, a pertinent question, especially since, as Radder himself affirms, no reproduction will be exactly the same as any other reproduction (1996: 82–83).