Summary During the 1930 and 1940s, the small world of cosmologists was buzzing with philosophical and methodological questions. The debate was stirred by Edward Milne's cosmological model, which was deduced from general principles that had no link with observation. Milne's approach was to have an important impact on the development of modern cosmology. But this article shows that it is an exaggeration to intimate, as some authors have done recently, that Milne's rationalism went on to infiltrate the discipline.

If you wish to learn from the theoretical physicist anything about the methods which he uses, I would give you the following piece of advice: Don't listen to his words, examine his achievements. For to the discoverer in that field, the constructions of his imagination appear so necessary and so natural that he is apt to treat them not as the creations of his thoughts but as given realities.

Recent results in kinematics, obtained by myself and those working with me, have convinced me that the philosophical status of physics, as it has come down to us from Renaissance days, requires reconsideration. The reason can be stated in a couple of sentences: it has been found possible to establish certain laws of physics—laws of motion, the law of gravitation, the laws known under the name of the Lorentz transformation, and some others—purely deductively, without specific assumptions, and without empirical appeals (...) save only to the empirical awareness of something we call “the passage of time.” Yet physicists have claimed ad nauseam that the ultimate sanction for “laws of nature” is observation and experiment, that this is what distinguishes physics from other branches of exact inquiry. The contrast in these two conceptions of natural law needs no emphasis. It is the purpose of this article to attempt to clarify this confused situation. (shrink)

In this paper I attempt to trace certain aspects of the evolution of theories of space-time and mechanics as revealed by a brief comparative study of Newtonian theory, Robb's theory, general relativity, and Milne's kinematical relativity. The first object is to emphasise how each theory leaves us in a position in which the succeeding one appears as a perfectly natural next step in the development of ideas. The second object is to show how, in spite of superficial differences in character, (...) the theories all necessarily possess the same general structure constituted by the presence of hypotheses, from which certain general mathematical relations are deduced, which in their turn are used to predict relations between observable quantities. (shrink)

When I agreed to lecture to-night I stipulated that I might be allowed to interpret the subject announced so as to let my treatment relate less to the subject in general than to some particular aspects which happen to have been interesting me lately. Professor Whitehead, Sir Arthur Eddington, and Sir James Jeans have given to the world brilliant accounts of the present position of physics in relation to mathematics and philosophy. What I have to say bears to their writings, (...) the humble relation of an example to a piece of book-work, or of an application of a theorem to the theorem itself. (shrink)