Furthermore there are alternative time-systems, but there is only one definite spatial order in each instantaneous space.

Accordingly the various modes of deriving spatial order from diverse time-systems must harmonise with one spatial order in each instantaneous space.

In this way also diverse time-orders are comparable.
We have two great questions still on hand to be settled before our theory of space is fully adjusted.

One of these is the question of the determination of the methods of measurement within the space, in other words, the congruence-theory of the space.

The measurement of space will be found to be closely connected with the measurement of time, with respect to which no principles have as yet been determined.