An 'infinite abstractive element deduced from the formative condition ' is the set of events which are members of -antiprimes, where is a formative condition regular for antiprimes. The element is said to be 'deduced' from its formative condition . The abstractive elements are the set of finite and infinite abstractive elements. 32.2 An abstractive element deduced from a regular formative condition is such that every abstractive class formed out of its members either covers all -primes [element finite] or is covered by all -antiprimes [element infinite]. Thus it represents a set of equivalent routes of approximation guided by the condition that each route is to satisfy the condition . 32.3 An abstractive element will be said to 'inhere' in any event which is a member of it. Two elements such that there are abstractive classes covered by both are said to 'intersect' in those abstractive classes. One abstractive element may cover another abstractive element. The elements of the utmost simplicity will be those which cover no other abstractive elements. These are elements which in euclidean phrase may be said to be 'without parts and without magnitude.' It will be our business to classify some of the more important types of elements. The elements of the greatest complexity will be those which can cover elements of all types. These will be 'moments.' A point of nomenclature is important. We shall name individual abstractive elements by capital latin letters, classes of elements by capital or small latin letters, and also, as heretofore, events by small latin letters. will continue to denote the fundamental relation of extension from which all the relations here considered are derived. CHAPTER IX DURATIONS, MOMENTS AND TIME-SYSTEMS 33. Antiprimes, Durations and Moments. 33.1 Among the constants of externality discussed in Part II was the reference of events to durations which are, in a sense, complete wholes of nature. A duration has thus in some sense an unlimited extension, though it is bounded in its temporal extent. Although we have not yet in our investigation of distinguished between spatial and temporal extension, durations can nevertheless be defined in terms of by this unlimited aspect of their extents. Namely, we assume that there are no other events with the same unlimited property. Accordingly, any abstractive class which is composed purely of durations can only be covered by abstractive classes which also are composed purely of durations. 33.2 An abstractive class is called an 'absolute antiprime' when is itself one of the antiprimes which satisfy the formative condition of covering . In other words, an absolute antiprime is an abstractive class which covers every abstractive class which covers it.