Note II. The book is dominated by the idea [cf. 14.1] that the relation of extension has a unique preeminence and that everything can be got out of it. During the development of the theme, it gradually became evident that this is not the case, and cogredience [cf. 16.4] had to be introduced. But the true doctrine, that 'process' is the fundamental idea, was not in my mind with sufficient emphasis. Extension is derivative from process, and is required by it. This failure to insist properly on 'process' is the reason for the paradoxical air attaching to the statement that 'objects are only derivatively in space and time by reason of their relations to events' [cf. 15.2]. Objects are of course essential for process, as appears clearly enough in the course of any analysis of process. But it is evident that particular times cannot result from the mere relations between objects which are at all times; and analogously for space. Accordingly space and time must result from something in process which transcends objects. But natural objects require space and time, so that space and time belong to their relational essence without which they cannot be themselves. In 15.4 it is pointed out that it is viâ objects that the concept of possibility has application. This suggestion requires further elaboration which cannot be attempted here. Similarly in 15.8, it is pointed out that continuity is derived from events, and atomicity from objects. This also requires development. It must suffice for the moment to suggest that a scientific object is an atomic structure imposed upon the continuity of events. Part II should be read in connection with Part IV at the end of the book. Note III. Chapter VI is made clearer by noting that the present duration [cf. 16.2] is primarily marked out by the significance of an interconnected display of sensa and of other associated objects immediately apparent. The duration is the realisation of a social entity in which the sense-objects and perceptual objects [cf. 23.9] are ingredient. The antecedent physical objects [cf. 24.5] and scientific objects [cf. 25] which occasion the duration to be what it is are another story, and the persistent habit of muddling the two sets of entities in philosophy—following the lead of language—is the origin of much confusion. For example there are four distinct meanings according to which you can speak of a chair; you may mean (i) a collection of sense-data, or (ii) a perceptual object, or (iii) a physical object, or (iv) a collection of scientific objects, such as molecules or electrons. It will be noted that I now make a distinction between perceptual objects and physical objects, contrary to 24.5. Thus a physical object is a social entity resulting from scientific objects, and halfway towards a perceptual object.