  In an important review of the entire confused situation between kinematic relativity and relativistic cosmology, McVittie confessed that “experimentally it seems hopeless to discriminate between them…at present the choice is almost entirely a matter of personal taste” (McVittie 1934 p. 29). At almost the same time, de Sitter took on Milne in serious fashion (de Sitter 1934). Responding to Milne’s methodological challenge, he showed that, indeed, it is possible to formulate relativistic cosmology in axiomatic fashion, just as Milne had formulated kinematic relativity “from concepts.” But de Sitter explicitly rejected Milne’s philosophical use of the cosmological principle, “which asserts that statistically the world pictures of two different observers must be the same.” His objection is founded on the matter-of-fact that “we have, however, no means of communicating with other observers, situated on faraway stars, or moving with excessive velocities” (de Sitter 1934 p. 598). So much for rational principles as hypotheses!