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reduces nature to a qualitative variety and change, exhibiting quantitative constancy. In order that such a version of science shall yield a naturalistic philosophy, it is necessary to show that nature so construed coincides with knowable reality. This conclusion may be arrived at in one or both of two ways. It may be argued that the ultimate qualitative terms of experience are somehow physical, or at any rate such as to permit of being explained only in terms of physical theories; or it may be argued that physical theories are the only verifiable, and so the only valid, theories. In other words, the priority of physical science may be argued from the nature of fact or from the nature of method. The former of these motives is represented by 'sensationalism,' and the latter by "experimentalism." Sensationalism and experimentalism are ordinarily united; but owing to a characteristic difference of emphasis, Karl Pearson serves to illustrate the former, and Henri Poincaré the latter.
§ 8. It is Pearson's central contention that the truths of science are conceptions and inferences formed from senseThe Sensation- impressions. The external object, which "at alism of Karl first sight appears a very simple object," turns out to be a "construct" of sensible properties, "a combination of immediate with past or stored sense-impressions." So that the field of science is "the contents of the mind." The sense-impressions constitute the only subject-matter of thought, the only reality that is directly given. The mind is shut up to senseimpressions, as a hypothetical operator who has never been outside a central telephone exchange, is shut up to the messages received at the inner end of the wire. "Turn the problem round and ponder over it as we may, beyond the sense-impression, beyond the brain terminals of the sensory nerves, we cannot get." "The 'reality,' as the metaphysicians wish to call it, at the other end of the nerve, remains unknown, and is unknowable." 1
1 Karl Pearson: Grammar of Science, second edition, pp. 39, 41, 75, 61, 63, 67.
These sense-impressions it is the business of science to "classify and analyze, associate, and construct." The "law of nature" is "a résumé in mental shorthand, which replaces for us a lengthy description of the sequences among our sense-impressions." "The object served by the discovery of such laws is the economy of thought." They enable the exertion, best calculated to preserve the race and give pleasure to the individual, to follow on the sense-impression with the least expenditure of time and of intellectual energy." A scientific concept such, for example, as the atom,' is either "real, that is, capable of being a direct sense-impression, or else it is ideal, that is, a purely mental conception by aid of which we are enabled to formulate natural laws." There is no ground for the assertion of an existence that is both "supersensuous" and also "real." 1
Pearson thus apparently accepts the analysis of physical substances and forces into non-physical terms. And yet he finds this view to afford sufficient ground for claiming the universal and exclusive validity of natural science and according metaphysics the doubtful honor of being ranked with poetry. Now upon further examination it appears that this conclusion is due to the fact that "sense-impressions" are not after all the ultimate terms of analysis, but are themselves, in Pearson's sense, physical “constructs." In regarding them as the ultimate terms of analysis, Pearson is virtually assuming the priority of the physical order. The sense-impression is a derivative of the whole naturalistic scheme, and means nothing apart from that scheme. "What we term the sense-impression " is conveyed by a sensory nerve, and is "formed at the brain." "A physical impress is the source of our stored sense-impression." The sameness of the external world depends on "the similarity in the organs of sense and in the perceptive faculty of all normal human beings"; and the consciousness of others is inferred from "physiological machinery of a • Ibid., Ch. I, passim.
1 Ibid., pp. 66, 86, 78, 67, 96.
certain character, which we sum up under brain and nerves." The "sequences of sense-impressions," "the routine of our perceptions," are not only functions of physiological nervestimulation, but may be conceived to have evolved as aids in "the struggle for existence." 1 It is perfectly evident, in short, that sense-impressions, in their structure and given order, presuppose the whole physical system. The real question is not how we can get "beyond the brain terminal," but how we ever came to be shut up to it. And the answer is, that in Pearson's philosophy we assume a physiological relativism, and the whole physical world-order in terms of which such a relativism is defined.
§ 9. Much light is thrown on the dogmatic character of Pearson's naturalism by the modified position of Ernst Mach. According to this author, the physical order is essentially a relationship sustained by more primitive elements. "A color is a physical object so long as we consider its dependence upon its luminous source, upon other colors, upon heat, upon space, and so forth. Regarding, however, its dependence upon the retina (the elements K L M . . .), it becomes a psychological object, a sensation." The bare color is neither physical nor psychical. A bullet, for example, turns yellow before a sodium lamp, red before a lithium lamp. Such a type of relationship may be represented by the symbols A B C. . . . But if we close the eyes or cut the optic nerve, the bullet disappears. So the bullet is also a function of a peculiar complex, the nervous system, represented by the symbols K L M. . "To this extent, and to this extent only, do we call A B C . . . sensations, and regard A B C as belonging to the ego." In other words, A B C ... are psychical only in so far as they belong to the specific system A B C ... KLM.... And similarly, volitions, memory-images and the like, represented by the symbols a ẞ y owe their distinctive character to the arrangement in which they are united. "The fundamental 1 Ibid. pp. 42, 63, 57, 86, 99, 103.
constituents of ABC ... a ẞy ... would seem to be the same (colors, sounds, spaces, times, motor sensations . . .), and only the character of their connexion different." In other words, not only "thing, body, matter," but also "perceptions, ideas, volition, and emotion, in short the whole inner and outer world, are composed of a small number of homogeneous elements connected in relations of varying evanescence or permanence.” 1
Now it is evidently improper to designate these elements themselves as "sensations," since a sensation is but one of the complex arrangements in which they appear. "Usually," says Mach, "these elements are called sensations. But as vestiges of a one-sided theory inhere in that term, we prefer to speak simply of elements (elementen)." He continues, it is true, to speak of bodies as "complexes of sensations," or definite connexions of "the sensory elements," and is thus in a measure responsible for the misunderstanding on which Pearson's sensationalism is based." But it is evident that Mach's view can only mean a reduction of both the physical and the mental order to a manifold of neutral elements; that is, elements which are neither physical nor mental. Nor can it be said of these elements that they are inherently disposed to those particular relationships and arrangements in which they compose bodies or physical events. The orders of logic and mathematics, of mind and of conduct, stand upon the same footing as those of mechanical nature. So the analytical method inevitably leads beyond naturalism to a 'logical realism,' that is as independent of physics as it is of psychology.' § 10. Thus critical naturalism, while it is successful in its polemic against every metaphysics of substance, fails thus far to establish itself. Its critical motive triumphs at the expense of its naturalistic motive. There remains, however, another
The Experimentalism of H. Poincaré
1 E. Mach: Analysis of Sensations, trans. by C. M. Williams, pp. 13-14, 17-18, 6, 18.
Ibid. pp. 18, 192.
Cf. below, pp. 310-311, 315-316.
ground on which its claims may be urged. Even though analysis may show that the primitive realities are not physical, it may yet be argued that the physical hypothesis is the only verifiable hypothesis, and that the truths of physical science are the only well-authenticated truths. In other words, naturalism may be argued, not on ground of fact, but on ground of method. Thus, for example, Pearson himself asserts that "the unity of all science consists alone in its method, not in its material," and that if any fields lie beyond science, they "must lie outside any intelligible definition which can be given of the word knowledge."1
The most notable contemporary representative of methodological naturalism or experimentalism, is Henri Poincaré. This writer's view is best comprehended in the light of its relation to the radical view of another contemporary French thinker, Edouard LeRoy. The latter, adopting the extreme 'anti-intellectualistic' position, insists upon the entire artificiality or conventionality of science, both in respect of its facts and its laws. Science is an invention for the purpose of action; and cannot, therefore, be regarded as a revelation of reality. It follows that action is prior to nature; and that action, since to define is to reconstruct and falsify, can be known only by instinct or intuition. It is evident that such a conclusion is not naturalistic; and Poincaré, in the interests of naturalism, properly undertakes to criticise it. If naturalism is to be maintained, facts cannot be regarded as wholly indeterminate, for that would imply the deriving of physical nature wholly from subjective activity. It would then follow that will is prior to body, and teleology to mechanism. It is necessary, therefore, to reserve for facts just enough determinateness to require the physical hypothesis and method
1 Op. cit., pp. 12, 15.
* See E. LeRoy: "Science et Philosophie," Revue de Métaphysique et de Morale, vol. VII, 1899, pp. 375 sq. Cf. Poincaré: The Value of Science, trans. by G. B. Halsted, pp. 112-114. For a discussion of 'anti-intellectualism,' see below, Ch. X.