with the moments of
, and thus each of these rects occupies
.
46.4 There are three different types of meaning which can be given to the idea of 'space' in connection with external nature, (i) There is the four-dimensional space of which event-particles are the points and the rects and point-tracks and null-tracks are the straight lines. In the geometry of this space there is a lack of uniformity between the congruence theories for rects and for point-tracks, and no such theory for null-tracks, (ii) There are the three-dimensional momentary (instantaneous) spaces in the moments of any time-system
, of which event-particles are the points and rects are the straight lines. The observed space of ordinary perception is an approximation to this exact concept, (iii) There is the time-less three-dimensional space of the time-system