Consider four moments which constitute an instance of case (iv). Let be the level which is the intersection of and , and let be the rect which is the intersection of . Then the rect does not lie in the level . The rect intersects the level in the common intersection of the four moments. This common intersection is an instantaneous point in the instantaneous spaces of the moments. In accordance with our practice of avoiding the conventional spatial terms when speaking of an instantaneous space, we have called this intersection a 'punct.' Since space is three-dimensional, any moment either covers every member of a given punct or covers none of its members. A punct represents the ideal of the maximum simplicity of absolute position in the instantaneous space of a moment in which it lies. 35.4 It is tempting, on the mathematical analogy of four-dimensional space, to assert the existence of unlimited events which may be called the complete intersections of pairs of non-parallel durations. It is dangerous however blindly to follow spatial analogies; and I can find no evidence for such unlimited events, forming the complete intersections of pairs of intersecting durations, except in the excluded case of parallelism when the complete intersection (if it exist) is itself a duration. Accordingly, apart from parallelism, it may be assumed that the events extended over by a pair of intersecting durations are all finite events. No change in the sequel is required if the existence of such infinite events be asserted. 36. Parallelism and Order. 36.1 Two levels which are the intersections of one moment with two parallel moments are called 'parallel.' Two parallel levels do not intersect, and conversely two levels in the same moment which do not intersect are parallel. 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 and , and ′ of moments ′ and ′, where is parallel to ′ and to ′: (ii) Two rects, and ′, are parallel if is the intersection of co-momental levels and , and ′ of comomental levels ′ and ′, where is parallel to ′ and to ′. A moment and a rect which do not intersect are parallel. A rect either intersects a moment in one punct, or is parallel to it, or is contained in it.