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.