Note IV. The attempt in [§ 33] to define a duration merely by means of its unlimitedness is a failure. In a note to the Concept of Nature, I point out that there is an analogous unlimitedness through time, corresponding to the spatial unlimitedness of a duration. Both unlimitednesses arise from the uniform significance of spatial extension for one, and of temporal extension for the other. Thus there is a temporal unlimitedness arising from a stationary event [cf. [§ 41]] in a definite space-time system. A point-track is the outcome of such an unlimitedness deprived of all spatial extension. But of course a point-track is a mere limit arrived at by the method of extensive abstraction. But I still hold to [§ 35.4].
Note V. In [§ 47] the concept of normality is explained with unnecessary elaboration. Let
and
be two intersecting moments belonging to diverse space-time systems
and
. Thus intersection of