A Reservation relative to the Psychical Order.—The scientific mind has shown in every age a real predilection towards the mechanical or materialistic theory. Contemporary scientists as a whole have accepted it in so far as it blends the vital and the physical orders. Objections and contradictions are only offered in the realm of psychology. A. Gautier, for example, has contested with infinite originality and vigour the claims of the materialists who would reduce the phenomenon of thought to a material phenomenon. The most general characteristic of material phenomenality is—as we shall later see—that it may be considered as a mutation of energy—i.e., it obeys the laws of energetics. Now thought, says A. Gautier, is not a form of material energy. Thought, comparison, volition, are not acts of material phenomenality; they are states. They are realities; they have no mass; they have no physical existence. They respond to adjustments, arrangements, and concerted groupings of material manifestations of chemical molecules. They escape the laws of energetics.
Kinetic Theory.—We shall lay aside for a moment this serious problem relative to the limits of the world of conscious thought and of the world of life. It is on the other side, on the frontiers of living and inanimate nature, that the mechanical view triumphs. It has furnished a universal conception agreeing with phenomena of every kind—viz., the kinetic theory, which ascribes everything in nature to the movements of particles, molecules, or atoms.
The living and the physical orders are here reduced to one unique order, because all the phenomena of the sensible universe are themselves reduced to one and the same mechanics, and are represented by means of the atom and of motion. This conception of the world, which was that of the philosophers of the Ionic school in the remotest antiquity, which was modified later by Descartes and Leibniz, has passed into modern science under the name of the kinetic theory. The mechanics of atoms ponderable or imponderable, would contain the explanation of all phenomenality. If it were a question of physical properties or vital manifestations, the objective world in final analysis would offer us nothing but motion. Every phenomenon would be expressed by an atomistic integral, and that is the inner reason of the majestic unity which reigns in modern physics. The forces which are brought into play by Life are no longer to be distinguished in this ultimate analysis from other natural forces. All are blended in molecular mechanics.
The philosophical value of this theory is undeniable. It has exercised on physical science an influence which is justified by the discoveries which it has suggested. But to biology, on the other hand, it has lent no aid. It is precisely because it descends too deeply into things, and analyzes them to the uttermost, that it ceases to throw any light upon them. The distance between the hypothetical atom and the apparent and concrete fact is too great for the one to be able to throw light on the other. The vital phenomenon vanishes with its individual aspect; its features can no longer be distinguished.
Besides, a whole school of contemporary physicists (Ostwald of Leipzig, Mach of Vienna) is beginning to cast some doubt on the utility of the kinetic hypothesis in the future of physics itself, and is inclined to propose to substitute for it the theory of energetics. We shall see, in every case, that this other conception, as universal as the kinetic theory, the theory of Energy, causes a vivid light to penetrate into the depths of the most difficult problems in physiology.
Such are, with their successive transformations, the three principal theories, the three great currents between which biology has been tossed to and fro. They are sufficiently indicative of the state of positive science in each age, but one is astonished that they are not more so; and this is due to the fact that these conceptions are too general. They soar too high above reality. More characteristic in this respect will be particular theories of the principal manifestations of living matter, of its perpetuity by generation, of the development by which it acquires its individual form, on heredity. It is here that it is of importance to grasp the progressive march of science—that is to say, the design and the plan of the building which is being erected, “blindly, so to speak,” by the efforts of an army of workers, an army becoming more numerous day by day.
CHAPTER V.
THE EMANCIPATION OF SCIENTIFIC RESEARCH FROM THE YOKE OF PHILOSOPHICAL THEORIES.
The excessive use of Hypothetical Agents in Physiological Explanations—§ 1. Vital Phenomena in Fully-constituted Organisms—Provisory Exclusion of the Morphogenic idea—The Realm of the Morphogenic Idea as the Sanctuary of Vital Force—§ 2. The Physiological Domain properly so called—Harmony and Connection of Phenomena—Directive Forces—Claude Bernard’s Work—Exclusion of Vital Force, of Final Cause, of the “Caprice” of Living Nature—Determinism—The Comparative Method—Generality of Vital Phenomena—Views of Pasteur.
The theories whose history we have just sketched in broad outline long dominated science and exercised their influence on its progress.
This domination has ceased to exist. Physiology has emancipated itself from their sway, and this, perhaps, is the most important revolution in the whole history of biology. Animism, vitalism, materialism, have ceased to exercise their tyranny on scientific research. These conceptions have passed from the laboratory to the study; from being physiological, they have become philosophical.