In any moment there will be a complete system of levels parallel to a given level in that moment, and such levels will be parallel to each other.
Similarly 'parallel' rects are defined by the intersection of parallel levels with a given level, all in one moment. Thus within any moment the whole theory of euclidean parallelism (so far as it is non-metrical) follows, and need not be further elaborated except to note the existence of parallelograms.
36.2 The definitions of parallel levels and of parallel rects can be extended to include levels and rects which are not co-momental:
(i) Two levels,
and
′ are parallel if
is the intersection of moments