3 2 D O C U M E N T 6 R E V I E W O F M E Y E R S O N deductive-constructive, highly abstract character of the theory, but rather he finds that this character corresponds to the tendency of the whole development of the exact sciences this tendency relinquishes more and more the convenience of fun- damentals and methods (in the psychological sense), in order to achieve a unity of the whole system in a logical sense. This deductive-constructive character impels Meyerson to compare the theory of relativity in a rather ingenious manner with the systems of Hegel and of Descartes. The success with contemporary thinkers of all three theories is attribut- ed to their logical completeness and their deductive character the human mind strives not only to establish relationships, but also to comprehend.[11]The advan- tage of the theory of relativity with respect to the other two theories mentioned is seen by Meyerson to lie in its quantitative structure and in its compatibility with a large number of empirical facts. Meyerson sees another essential correspondence between Descartes’s theory of physical events and the theory of relativity, namely the reduction of all concepts of the theory to spatial, or rather geometrical, con- cepts however this is presumed to apply completely to the theory of relativity only after the electric field has been subsumed into the theory in the manner of Weyl’s or Eddington’s theory. I would like to consider this latter point in some more detail, since my opinion differs strongly here. To be specific, I cannot admit that the assertion that relativity theory traces physics back to geometry has a clear meaning.[12] It would be more correct to say that the theory of relativity has been accompanied by a loss of the special status of (metric) geometry relative to those regularities that were always considered to be physical.[13] Even before the proposal of the theory of relativity, it was not justifiable to consider geometry as an a priori doctrine as compared to physics. This occurred simply because one usually forgets that geometry is the study of the possible positional properties of rigid bodies. According to the general theory of relativity, the metric tensor determines the behavior of the measuring rods and clocks as well as the motion of free bodies in the absence of electrical effects. The fact that the metric tensor is denoted as “geometrical” is due simply to the fact that this formal structure first appeared in the area of study denoted as “geometry.” However, this by no means justifies calling every science in which that formal structure plays a role a “geometry,” not even when for the sake of illustration one makes use of concepts familiar from geometry. With similar arguments, Maxwell and Hertz could have termed the electromagnetic equations for the vacuum “geo- metric” because the geometrical concept of the vector occurs in them.[14] It is, by the way, gratifying to me to emphasize that Meyerson himself states expressly in his last chapter that applying the terminology “geometric” to the theory of relativity is in fact unsubstantial one could just as well say that the metric tensor describes the “state of the ether.”[15]