II.
Like the other fundamental sciences Biology must be abstract, that is to say it must not bear upon individual beings, but upon phenomena. It is thus distinct from zoology and botany which are concrete sciences. In its widest generality it is defined through the constant correspondence between the anatomical and the physiological point of view. Its object is to constantly unite them to one another. In reality these two points of view are the two aspects of a single problem. It is owing to historical reasons that, during a certain time, these two sciences appeared to develop independently of one another. Physiology remained attached to the metaphysical methods, that is to say, to unverifiable hypotheses and to principles which went beyond experience, while anatomists already made use of the positive method. But to-day, the two sciences being equally positive, “their opposition is reduced to that which subsists between the static and the dynamic points of view.”[156]
Another element which should enter into the more general definition of biology, although it has sometimes been neglected, is the consideration of the milieu. The relation between the organism and its milieu is no less essential to life than the relation of the organ to the function. Life supposes not only that the being should be organised in a certain way, but also that a certain number of external circumstances should sustain this organisation, and should be compatible with its activity. Living beings are thus dependent upon their milieu, and this dependence grows as we rise in the organic series. The system of the conditions of existence becomes all the more complex as the functions develop and become more varied. Inferior organisms are subject to less numerous external conditions; but, says Comte, a little variation in one of these conditions suffices to make them perish. The superior organisms stand a variation of this kind better. But, in return, the number of conditions upon which they depend is far greater. The study of milieux in their relations to organisms, a study which is hardly outlined, undoubtedly has many discoveries in store for the future.[157] Here is an order of problems of which Lamarck probably suggested the idea to Comte, and upon which Darwin’s genius will work.
Bichat then was wrong in saying in his celebrated definition of life that it is “the sum of the forces which resist death.” The radical antagonism between inorganic and living nature is an incomplete and consequently a false idea. Indeed if, as Bichat supposed, everything which surrounds living bodies tended to destroy them, their existence would become unintelligible.[158] Where could they find strength to resist such formidable pressure, even for a short time? On the contrary, the fundamental condition for life is a certain “harmony” between the organism and the milieu in which it is placed. The proof of this is furnished at every turn by experience.
This being established, what will be the most general problem of the science of life? From the anatomical point of view, says Comte, all possible organisms, all parts whatever of each organism, and all the various states of each necessarily present a common basis of structure and of composition, from which the tissues, organs and apparatus have emerged by means of a progressive differentiation. In the same way, from the physiological point of view, all living beings, from the vegetable kingdom up to man, considered in all their actions and all the periods of their existence, necessarily possess a common basis of vital activity, whence the innumerable phenomena of nutrition, secretion, etc., proceed, by means of progressive differentiation. Now, from both these points of view, that which is similar in these cases, is more important than that which distinguishes them, since the more general phenomena govern those which are less so. We must therefore disengage the elementary physiological phenomenon and the anatomical structure which corresponds to it, we must determine their relation, and, with the help and confirmation of experience, we must deduce the increasingly more complex, physiological and anatomical, phenomena from it.[159]
This conception which, despite Comte’s reservation, still appears to be entirely saturated with the Cartesian spirit, leads him to the “most mathematical statement possible” of the biological problem. “Given the organ, or the organic modification, to find the function or the act, and vice versa.”[160] There is nothing more in conformity with the general definition of science, which consists in substituting the knowledge of laws to that of facts, and rational prevision to empirical observation. Here, it is true, we have an “ideal scientific type,” from which biology, which has scarcely reached the positive state, is very far removed. But there is no science which does not fall short of its definition more or less. The use of this definition is already a help for a science, and provides a means for measuring its progress.