Note 9 — Chapter III · DETAILED CONSIDERATION OF VARIOUS CONCEPTS OF PHYSICS

We must include in general in the concept of "initial condition" the past history of the system. In order not to make this condition so broad as to defeat itself, we have to add the observation that actually identity of past history is necessary over only a comparatively short interval of time. Logical precision seems unattainable here—the physical concepts themselves have not the necessary precision.