1 3 0 D O C . 1 3 1 D I S C U S S I O N O N R E L A T I V I T Y Mr. Einstein. — Regarding Kant’s philosophy, I believe that each philosopher has his own Kant and so I could not respond to what you just said because the few indications you gave do not suffice for me to know how you interpret Kant. I, for my part, do not believe that my theory harmonizes on all points with Kant’s thought as I see it. What appears most important to me in Kant’s philosophy is its mention of a pri- ori concepts to construct science. Thus one can contrast two points of view: Kant’s apriorism, in which certain concepts preexist in our consciousness, and Poincaré’s conventionalism. These two points of view concur about the point that science needs arbitrary concepts to build upon whereas I can say nothing about knowing whether these concepts are a priori givens or are arbitrary conventions. [. . .] Mr. Einstein. — So the question can be posed thus: Is a philosopher’s time the same as a physicist’s? A philosopher’s time, I believe, is both a psychological and a physical time consequently physical time may be derived from the time in the conscience. Individuals have a primitive notion of the simultaneity of perception so they can confer among themselves and decide on something they perceive this would be a first stage toward objective reality. However, there are objective events independent of individuals and so the advance was made from the simultaneity of perceptions to that of the events themselves. And, in fact, for a long time this simul- taneity did not lead to any contradictions because of the great velocity at which light propagates. So the concept of simultaneity was able to bypass the perceptions to the objects. From there it was not far removed to deduce a temporal order among events and instinct did so. Yet nothing in our conscience permits us to conclude the simultaneity of events, because these are no more than mental constructions, logi- cal entities. Consequently, there is no such thing as a philosopher’s time there is only a psychological time differing from a physicist’s time. [. . .] Mr. Einstein. — In the four-dimensional continuum definitely not all directions are equivalent. On the other hand, from the logical point of view there does not seem to be much relation between the theory of relativity and Mach’s theory. For Mach there are two points to distinguish: on one hand, there are things that we cannot budge: these are the immediate facts of experience on the other hand, these are concepts that we can, on the contrary, modify. Mach’s system studies the relations existing between the facts of experience the ensemble of these relations, for Mach, is science. This is a false standpoint here all in all, what Mach had made was a catalog, not a [p. 101] [p. 102] [p. 107] [p. 111] [p. 112]