Process and Reality — the Gifford Lectures, 1929

So far, starting from an actual occasion M, we find six loci, or types of loci, defined purely in terms of notions derived from ‘causal efficacy.’ These loci are, M’s causal past, M’s causal future, M’s contemporaries, the set of durations defined by M; and finally, taking any one such duration which we call D as typical, there is D’s past, and D’s future. Thus there are the three definite loci, the causal past, the causal present, and the contemporaries, which are defined uniquely by M; and there are the set of durations defined by M, and the set of ‘durational pasts’ and the set of ‘durational futures.’ The paradox which has been introduced by the modern theory of relativity is twofold. First, the actual occasion M does not, as a general characteristic of all actual occasions, define a unique duration; and secondly such a unique duration, if defined, does not include all the contemporaries of M.

But among the set of durations, there may be one with a unique association with M. For the mode of presentational immediacy objectifies for M, the actual occasions within one particular duration. This is the ‘presented duration.’ Such a presented duration is an inherent factor in the character of an ‘enduring physical object.’ It is practically identical with the strain-locus. This locus is the reason why there is a certain absoluteness in the notions of rest, velocity, and acceleration. For this presented duration is the spatialized world in which the physical object is at rest, at least momentarily for its occasion M. This spatialized world is objectified for M by M’s own conditioned range of feeling-tones which have been inherited from the causal past of the actual occasionp. 489 in question, namely, of M. Thus the presented duration is with peculiar vividness part of the character of the actual occasion. A historic route of actual occasions each with its presented duration, constitutes a physical object.

Our partial consciousness of the objectifications of the presented duration constitutes our knowledge of the present world, so far as it is derived from the senses. Remembering that objectifications constitute the objective conditions from which an actual occasion (M/) initiates its successive phases of feeling, we must admit that, in the most general sense, the objectifications express the causality by which the external world fashions the actual occasion in question. Thus the objectifications of the presented duration represent a recovery by its contemporaries of a very real efficacy in the determination of M. It is true that the eternal objects which effect this objectification belong to the feeling-tones which M derives from the past. But it is a past which is largely common to M and to the presented duration. Thus by the intermediacy of the past, the presented duration has its efficacy in the production of M. This efficacy does not derogate from the principle of the independence of contemporary occasions. For the contemporary occasions in the presented duration are only efficacious through the feeling-tones of their sources, and not through their own immediate fecling-tones.

Thus in so far as Bergson ascribes the ‘spatialization’ of the world to a distortion introduced by the intellect, he is in error. This spatialization is a real factor in the physical constitution of: every actual occasion belonging to the life history of an enduring physical object. For actual occasions in so-called ‘empty space,’ there is no reason to believe that any duration has been singled out for spatialization; that is to say, that physical perception in the mode of presentational immediacy is negligible for such occasions. The reality of the rest and the motion of enduring physical objects depends on this spatializap. 490tion for occasions in their historic routes. The presented duration is the duration in respect to which the enduring object is momentarily at rest. It is that duration which is the strain-locus of that occasion in the life-history of the enduring object.

CHAPTER V
MEASUREMENT

SECTION I

THE identification of the strain-locus with a duration is only an approximation based upon empirical evidence. Their definitions are entirely different. A duration is a complete set of actual occasions, such that all the members are mutually contemporary one with the other. This property is expressed by the statement that the members enjoy ‘unison of immediacy.’ The completeness consists in the fact that no other actual occasion can be added to the set without loss of this unison of immediacy. Every occasion outside the set is in the past or in the future of some members of the set, and is contemporary with other members of the set. According as an occasion is in the past, or the future, of some members of a duration, the occasion is said to be in the past, or in the future, of that duration.

No occasion can be both in the past and in the future, of a duration. Thus a duration forms a barrier in the world between its past and its future. Any route of occasions, in which adjacent members are contiguous, and such that it includes members of the past, and members of the future, of a duration, must also include one or more members of that duration. This is the notion of a duration, which has already been explained (cf. Part II, Ch. IV, Sects. VIII and IX).

The definition of a strain-locus (cf. previous chapter) depends entirely on the geometrical elements which are the elements of geometric form in the objectification of a nexus including the experient occasion in question. Thesep. 491p. 492 elements are (i) a set of points, within the volume of the regional standpoint of the experient occasion, and (11) the set of straight lines defined by all the pairs of these points. The set of points is the ‘seat’ of the strain; the set of straight lines is the set of ‘projectors.’ The complete region penetrated by the ‘projectors’ is the strainlocus. A strain-locus is bounded by two ‘flat’ threedimensional surfaces. When some members of the seat have a special function in the strain-feeling, the projectors which join pairs of these points may define a subordinate region in the strain-locus; this subordinate region is termed the ‘focal region.’