Process and Reality — the Gifford Lectures, 1929

trated by the sensa; while the causal past, the causal future, and the other contemporary events, are only indirectly perceived by means of their extensive relations to the presented locus. It must be remembered that the presented locus has its fourth dimension of temporal thickness ‘spatialized’ as the specious present of the percipient. Thus the presented locus, with the animal body of the percipient as the region from which perspectives are focussed, is the regional origin by reference to which in this perceptive mode the complete scheme of extensive regions isrendered determinate. The respective roles of the two perceptive modes in experience are aptly exemplified by the fact that all scientific observations, such as measurements, determinations of relative spatial position, determinations of sense-data such as colours, sounds, tastes, smells, temperature feelings, touch feelings, etc., are made in the perceptive mode of presentational immediacy; and that great care is exerted to keep this mode pure, that is to say, devoid of symbolic reference to causal efficacy. In this way accuracy is secured, in the sense that the direct observation is purged of all interpretation. On the other hand all scientific theory is stated in terms referring exclusively to the scheme of relatedness, which, so far as it is observed, involves the percepta in the pure mode of causal efficacy. It thus stands out at once, that what we want to know about, from the point of view either of curiosity or of technology, chiefly resides in those aspects of the world disclosed in causal efficacy: but that what we can distinctly register is chiefly to be found among the percepta in the mode of presentational immediacy.

The presented locus is a common ground for the symbolic reference, because it is directly and distinctly perceived in presentational immediacy, and is indistinctly and indirectly perceived in causal efficacy. In the latter mode, the indistinctness is such that the detailed geometrical relationships are, for the most part, incurably vague. Particular regions are, in this perceptive mode,

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in general not distinguishable. In this respect, causal efficacy stands in contrast to presentational immediacy with its direct illustration of certain distinct regions. But there are exceptions to this geometrical indistinctness of causal efficacy. In the first place, the separation of the potential extensive scheme into past and future lies with the mode of causal efficacy and not with that of presentational immediacy. The mathematical measurements, derivable from the latter, are indifferent to this distinction; whereas the physical theory, expressed in terms of the former, is wholly concerned with it. In the next place, the animal body of the percipient is a region for which causal efficacy acquires some accuracy in its distinction of regions—not all the distinctness of the other mode, but sufficient to allow of important identifications. For example, we see with our eyes, we taste unth our palates, we touch with our hands, ete.: here the causal efficacy defines regions which are identified with themselves as perceived with greater distinctness by the other mode. To take one example, the slight eye-strain in the act of sight is an instance of regional definition by presentational immediacy. But in itself it is no more to be correlated with projected sight than is a contemporary stomach-ache, or a throb in the foot. The obvious correlation of the eye-strain with sight arises from the perception, in the other mode, of the eye as efficacious in sight. This correlation takes place in virtue of the identity of the two regions, the region of the eye-strain, and the region of eye-efficacy. But the eye-strain is so immeasurably the superior in its power of regional definition that, as usual, we depend upon it for explicit geometrical correlations with other parts of the body. In this way, the animal body is the great central ground underlying all symbolic reference. In respect to bodily perceptions the two modes achieve the maximum of symbolic reference, and pool their feelings referent to identical regions. Every statement about the geometrical relationships of physical bodies in the world is ultimatelyp. 259 referable to certain definite human bodies as origins of reference. A traveller, who has lost his way, should not ask, Where am I? What he really wants to know is, Where are the other places? He has got his own body, but he has lost them.

SECTION II

The second ‘ground’ for symbolic reference is the connection between the two modes effected by the identity of an eternal object ingredient in both of them. It will be remembered that the former ‘ground’ was the identity of the extensive region throughout such stages of direct perception and synthesis, when there was a diversity of eternal objects, for example, eye-region, visual sensa, eyestrain. But now we pass to a diversity of regions combined with an identity of the eternal object, for example, visual sensa given by efficacity of eye-region, and the region of the stone perceived in the mode of presentational immediacy under the illustration of the same visual sense. In this connection the ‘make-believe’ character of modern empiricism is well shown by putting into justaposition two widely separated passages’ from Hume’s Treatise: “Impressions may be divided into two kinds, those of sensation, and those of reflection. The first kind arises in the soul originally, from unknown causes.”’ And “Tf it be perceived by the eyes, it must be a colour; .. .”

The earlier passage is Hume’s make-believe, when he is thinking of his philosophical principles. He then refers the visual sensations ‘in the soul’ to ‘unknown causes.’ But in the second passage, the heat of argument elicits his real conviction—everybody’s real conviction—that visual sensations arise ‘by the eyes.’ The causes are not a bit ‘unknown,’ and among them there is usually to be found the efficacity of the eyes. If Hume had stopped to investigate the alternative causes for the occurrence of visual sensations—for example, eye-sight, or excessive consumption of aleohol—he might have hesitated in his

1Cf. Book I, Part I, Sects. II and VI (italics mine).

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profession of ignorance. If the causes be indeed unknown, it is absurd to bother about eye-sight and intoxication. The reason for the existence of oculists and prohibitionists is that various causes are known.