Criticisms of the Mechanistic Theory of Life.
The course of the mechanistic theory of life has been surprisingly similar to that of its complement, the theory of the general evolution of the organic world. [pg 235] The two great doctrines of the schools, Darwinism on the one hand, the mechanical interpretation of life on the other, are both tottering, not because of the criticism of outsiders, but of specialists within the schools themselves. And the interest which religion has in this is the same in both cases: the transcendental nature of things, the mysterious depth of appearance, which these theories denied or obscured, become again apparent. The incommensurableness and mystery of the world, which are, perhaps, even more necessary to the very life of religion than the right to regard it teleologically, reassert themselves afresh in the all-too-comprehensible and mathematically-formulated world, and re-establish themselves, notwithstanding obstinate and persistent attempts to do away with them. This is perhaps to the advantage of both natural science and religion: to the advantage of religion because it can with difficulty co-exist with the universal dominance of the mathematical way of looking at things; to the advantage of natural science because, in giving up the one-sidedness of the purely quantitative outlook, it does not give up its “foundations,” its “right to exist,” but only a petitio principii and a prejudice that compelled it to exploit nature rather than to explain it, and to prescribe its ways rather than to seek them out.
The reaction from the one-sided mechanical theories shows itself in many different ways and degrees. It may, according to the individual naturalist, affect the [pg 236] theory as a whole, or only certain parts of it, or only particular lines. It starts with mere criticism and with objections, which go no further than saying that “in the meantime” we are still far from having reached a physico-chemical solution of the riddle of life; it may ascend through all stages up to an absolute rejection of the theory as an idiosyncrasy of the time which impedes the progress of investigation, and as an uncritical prejudice of the schools. It may remain at the level of mere protest, and content itself with demonstrating the insufficiency of the mechanical explanation, without attempting to formulate any independent theory for the domain of the vital; or it may construct a specifically biological theory, claiming independence amid other disciplines, and basing this claim on the autonomy of vital processes; or it may widen out deliberately into metaphysical study and speculation. Taken at all these levels it presents such a complete section of the trend of modern ideas and problems that it would be an attractive study even apart from the special interest which attaches to it from the point of view of religious and idealistic conceptions of the universe.
Both Liebig and Johannes Müller remained vitalists, notwithstanding the discovery of the synthesis of urea and the increasing number of organic compounds which were built up artificially by purely chemical methods. It was only about the middle of the last century that the younger generation, under the leadership, in Germany, of Du Bois-Reymond in particular, went over [pg 237] decidedly to the mechanistic side, and carried the doctrines of the school to ever fresh victories. But opposition was not lacking from the outset, though it was restrained and cautious.
Virchow's “Caution”.
Here, as also in regard to “Darwinism,” which was advanced about the same time, the typical advocate of “caution” was Rudolf Virchow. His doubts and reservations found utterance very soon after the theory itself had been promulgated. In his “Cellular Pathologie,”[76] and in an essay on “The Old Vitalism and the New,”[77] he puts in a word for a vis vitalis. The old vitalism, he declared, had been false because it assumed, not a vis, but a spiritus vitalis. The substances in animate and in inanimate bodies have undoubtedly absolutely the same properties. Nevertheless, “we must at once rid ourselves of the scientific prudery of regarding the processes of life solely as the mechanical result of the molecular forces inherent in their constituent bodily parts.” The essential feature of life is a derived and communicated force additional to the molecular forces. Whence it comes we are not told. He glided all round the problem with platitudinarian expressions, which were intended to show his own adherence as a matter of course to the new biological school, and which revealed at the same time his striking incapacity for defining a [pg 238] problem with any precision. At a “certain period in the evolution of the earth” this force arose, as the ordinary mechanical movements “swung over” into the vital. But it is thus a special form of movement, which detaches itself from the great constants of general movement, and runs its course alongside of, and in constant relation to, these. (Did ever vitalist assert more?) After thus preparing the way for a return of the veering process at a particular stage of evolution, and giving the necessary assurances against the “diametrically opposed dualistic position,” Virchow employs almost all the arguments against the mechanical theory which vitalists have ever brought forward. Even the catalytic properties of ferments are above the “ordinary” physical and chemical forces. The movement of crystallisation, too, cannot be compared with the vital movement. For vital force is not immanent in matter, but is always the product of previous life.[78] In the simplest processes of growth and nutrition the vis vitalis plays its vital rôle. This is true in a much greater degree of the processes of development and morphogenesis. In the phenomena of irritability life reveals its spontaneity through “responses,” and so on. “Peu d'anatomie pathologique éloigne du vitalisme, beaucoup d'anatomie pathologique y ramène.”
It is impossible to make much of this position. It leaves the theory with one of the opposing parties, the [pg 239] practice with the other, and the problem just where it was before.