Williams and Norgate, 1917.
If A and B are two events, and A' is part of A and B' is part of B, then in many respects the relations between the parts A' and B' will be simpler than the relations between A and B.This is the principle which presides over all attempts at exact observation.
The first outcome of the systematic use of this law has been the formulation of the abstract concepts of Time and Space.

In the previous lecture I sketched how the principle was applied to obtain the time-series.

I now proceed to consider how the spatial entities are obtained by the same method.

The systematic procedure is identical in principle in both cases, and I have called the general type of procedure the 'method of extensive abstraction.' You will remember that in my last lecture I defined the concept of an abstractive set of durations.

This definition can be extended so as to apply to any events, limited events as well as durations.