Process and Reality — the Gifford Lectures, 1929

A complete region, satisfying the principle of ‘concrescent unison,’ will be called a ‘duration.’ A duration is a cross-section of the universe; it is the immediate present condition of the world at some epoch, according to the old ‘classical’ theory of time—a theory never doubted until within the last few years. It will have been seen that the philosophy of organism accepts and defines thisp. 191 notion. Some measure of acceptance is imposed upon metaphysics. If the notion be wholly rejected no appeal to universal obviousness of conviction can have any weight; since there can be no stronger instance of this force of obviousness.

The ‘classical’ theory of time tacitly assumed that a duration included the directly perceived immediate present of each one of its members. The converse proposition certainly follows from the account given above, that the immediate present of each actual occasion lies in a duration. An actual occasion will be said’* to be ‘congredient with’ or ‘stationary in’ the duration including its directly perceived immediate present. The actual occasion is included in its own immediate present; so that each actual occasion through its percipience in the pure mode of presentational immediacy—if such percipience has important relevance—defines one duration in which it is included. The percipient occasion is ‘stationary’ in this duration.

But the classical theory also assumed the converse of this statement. It assumed that any actual occasion only lies in one duration; so that if N lies in the duration including M’s immediate present, then M lies in the duration including N’s immediate present. The philosophy of organism, in agreement with recent physics, rejects this conversion; though it holds that such rejection is based on scientific examination of our cosmic epoch, and not on any more general metaphysical principle. According to the philosophy of organism, in the present cosmic epoch only one duration includes all M’s immediate present; this one duration will be called M’s ‘presented duration.’ But M itself lies in many durations; each duration including / also includes some portions of M’s presented duration. In the case of human perception practically all the important portions are thus included; also in human experience the relationship to such dura-

° Cf. my Principles of Natural Knowledge, Ch. XI, and my Concept of Nature, Ch. V.

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tions is what we express by the notion of ‘movement.’

To sum up this discussion. In respect to any one actual occasion WM there are three distinct nextis of occasions to be considered:

(i) The nexus of M’s contemporaries, defined by the characteristic that M and any one of its contemporaries happen in causal independence of each other.

(ii) Durations including M, any such duration is defined by the characteristic that any two of its members are contemporaries. (It follows that any member of such a duration is contemporary with M, and thence that such durations are all included in the locus (i). The characteristic property of a duration is termed ‘unison of becoming.’)

(i) M’s presented locus, which is the contemporary nexus perceived in the mode of presentational immediacy, with its regions defined by sensa. It is assumed, on the basis of direct intuition, that M’s presented locus is closely related to some one duration including M. It is also assumed, as the outcome of modern physical theory, that there is more than one duration including M. The single duration which is so related to M’s presented locus is termed ‘M’s presented duration.’ But this connection is criticized in the following sections of this chapter. In Part IV, the connection of these ‘presented’ loci to regions defined by straight lines is considered in more detail; the notion of ‘strain loci’ is there introduced.

SECTION Ix

Physical science has recently arrived at the stage in which the practical identification, made in the preceding section, between the ‘presented locus’ of an actual entity, and a locus in ‘unison of becoming’ with the actual entity must be qualified.

The two notions, ‘presented locus’ and ‘unison of becoming,’ are distinct. The identification merely rests on the obvious experience of daily life. In any recasting ofp. 198 thought it is obligatory to include the identification as a practical approximation to the truth, sufficient for daily life. Subject to this limitation, there is no reason for rejecting any distinction between them which the evidence suggests.

In the first place, the presented locus is defined by some systematic relation to the human body—so far as we rely, as we must, upon human experience. A certain state of geometrical strain in the body, and a certain qualitative physiological excitement in the cells of the body, govern the whole process of presentational immediacy. In sense-perception the whole function of antecedent occurrences outside the body is merely to excite these strains and physiological excitements within the body. But any other means of production would do just as well, so long as the relevant states of the body are in fact produced. The perceptions are functions of the bodily states. The geometrical details of the projected sense-perception depend on the geometrical strains in the body, the qualitative sensa depend on the physiological excitements of the requisite cells in the body.

Thus the presented locus must be a locus with a systematic geometrical relation to the body. According to all the evidence, it is completely independent of the contemporary actualities which in fact make up the nexus of actualities in the locus. For example, we see a picture on the wall with direct vision. But if we turn our back to the wall, and gaze into a good mirror, we see the same sight as an image behind the mirror. Thus, given the proper physiological state of the body, the locus presented in sense-perception is independent of the details of the actual happenings which it includes. This is not to say, that sense-perception is irrelevant to the real world. It demonstrates to us the real extensive continuum in terms of which these contemporary happenings have their own experiences qualified. Its additional information in terms of the qualitative sensa has relevance in proportion to the relevance of the immediate bodily state to the immep. 194diate happenings throughout the locus. Both are derived from a past which is practically common to them all. Thus there is always some relevance; the correct interpretation of this relevance is the art of utilizing the perceptive mode of presentational immediacy as a means for understanding the world as a medium.

But the question which is of interest for this discussion is how this systematic relevance, of body to presented locus, is definable. This is not a mere logical question. The problem is to point out that element in the nature of things constituting such a geometrical relevance of the body to the presented locus. If there be such an element, we can understand that a certain state of the body may lift it into an important factor of our experience.

The only possible elements capable of this extended systematic relevance beyond the body are straight lines and planes. Planes are definable in terms of straight lines, so that we can concentrate attention upon straight lines.

It is a dogma of science that straight lines are not definable in terms of mere notions of extension. Thus, in the expositions of recent physical theory, straight lines are defined in terms of the actual physical happenings. The disadvantage of this doctrine is that there is no method of characterizing the possibilities of physical events antecedently to their actual occurrence. It is easy to verify that in fact there is a tacit relevance to an underlying system, by reference to which the physical loci—including those ealled ‘straight lines—are defined. The question is how to define this underlying system in terms of ‘pure’ straight lines, determinable without reference to the casual details of the happenings.