to body. La Mettrie, a physician and the auth of a book entitled "L'Homme Machine,” was fr interested in this thesis by a fever delirium, a afterward adduced anatomical and pathologie. data in support of it. The angle from which b views human life is well illustrated in the for lowing:

"What would have sufficed in the case of Julius Cæsa of Seneca, of Petronius, to turn their fearlessness int timidity or braggartry? An obstruction in the spleer the liver, or the vena portae. For the imagination is intimately connected with these viscera, and from ther arise all the curious phenomena of hypochondria and hysteria. 'A mere nothing, a little fibre, some trifling thing that the most subtle anatomy cannot discover, would have made two idiots out of Erasmus and Fontenelle.'"' 15

§ 116. The extreme claim that the soul is a physical organ of the body, identical with the brain, marked the culmination of this militant materialism, so good an inEpiphenome- stance of that over-simplification and

Radical
Materialism.
Mind as an

non.

whole-hearted conviction characteristic of the doctrinaire propagandism of France. Locke, the Englishman, had admitted that possibly the substance which thinks is corporeal. In the letters of Vol

15 From the account of La Mettrie in Lange: History of Materialism. Translation by Thomas, II, pp. 67-68.

aire this thought has already found a more positive expression:

"I am body, and I think; more I do not know. Shall I then attribute to an unknown cause what I can so easily attribute to the only fruitful cause I am acquainted with? In fact, where is the man who, without an absurd godlessness, dare assert that it is impossible for the Creator to endow matter with thought and feeling?" 16 Finally, Holbach, the great systematizer of this movement, takes the affair out of the hands of the Creator and definitively announces that "a sensitive soul is nothing but a human brain so constituted that it easily receives the motions communicated to it." 17

This theory has been considerably tempered since the age of Holbach. Naturalism has latterly been less interested in identifying the soul with the body, and more interested in demonstrating its dependence upon specific bodily conditions, after the manner of La Mettrie. The so-called higher faculties, such as thought and will, have been related to central or cortical processes of the nervous system, processes of connection and complication which within the brain itself supplement the impulses and sensations congenitally and externally 16 Quoted from Voltaire's London Letter on the English, by Lange: Op. cit., II, p. 18.

17 Quoted by Lange: Op. cit., II, p. 113.

stimulated. The term "epiphenomenon ” has be adopted to express the distinctness but entire & pendence of the mind. Man is "a conscio automaton." The real course of nature pass through his nervous system, while consciousnes attends upon its functions like a shadow, presa but not efficient.18

Positivism and

§ 117. Holbach's "Système de la Nature,” putlished in 1770, marks the culmination of the ur Knowledge. equivocally materialistic form of natu Agnosticism. ralism. Its epistemological difficulties, always more or less in evidence, have since that day sufficed to discredit materialism, and to foster the growth of a critical and apologetic form of naturalism known as positivism or agnosticism. The modesty of this doctrine does not, it is true, strike very deep. For, although it disclaims knowledge of ultimate reality, it also forbids anyone else to have any. Knowledge, it affirms, can be of but one type, that which comprises the verifiable laws governing nature. All questions concerning

18 The phrase "psycho-physical parallelism," current in psychology, may mean automatism of the kind expounded above, and may also mean dualism. It is used commonly as a methodological principle to signify that no causal relationship between mind and body, but one of correspondence, is to be looked for in empirical psychology. Cf. § 99.

irst causes are futile, a stimulus only to excursions ɔf fancy popularly mistaken for knowledge. The superior certainty and stability which attaches to natural science is to be permanently secured by the savant's steadfast refusal to be led away after the false gods of metaphysics.

But though this is sufficient ground for an ag nostic policy, it does prove an agnostic theory. The latter has sprung from a closer analysis of knowledge, though it fails to make a very brave showing for thoroughness and consistency. The crucial point has already been brought within our view. The general principles of naturalism require that knowledge shall be reduced to sensations, or impressions of the environment upon the organism. But the environment and the sensations do not correspond. The environment is matter and motion, force and energy; the sensations are of motions, to be sure, but much more conspicuously of colors, sounds, odors, pleasures, and pains. Critically, this may be expressed by saying that since the larger part of sense-perception is so unmistakably subjective, and since all knowledge alike must be derived from this source, knowledge as a whole must be regarded as dealing only with appearances. There are at least three agnostic

All ag

methods progressing from this point. that the inner or essential reality is unfathomati But, in the first place, those most close to t tradition of materialism maintain that the me significant appearances, the primary qualities, ar those which compose a purely quantitative and corporeal world. The inner essence of things may at any rate be approached by a monism of matter or of energy. This theory is epistemological only to the extent of moderating its claims in the hope of lessening its responsibility. Another agnosticism places all sense qualities on a par, but would regard physics and psychology as complementary reports upon the two distinct series of phenomena in which the underlying reality expresses itself. This theory is epistemological to the extent of granting knowledge, viewed as perception, as good a standing in the universe as that which is accorded to its object. But such a dualism tends almost irresistibly to relapse into materialistic monism, because of the fundamental place of physical conceptions in the system of the sciences. Finally, in another and a more radical phase of agnosticism, we find an attempt to make full provision for the legitimate problems of epistemology. The only datum, the only existent accessible to knowledge,