which, though very diverse, present no definite combinations. Its composition, no doubt, is definite, and equally so its properties; but they are variable, and its variations alter the relations of the environment to the living being. To all changes of the environment there are corresponding changes in the living being, otherwise it would perish. These changes, which follow the laws of vital changes, inasmuch as they are in a definite combination, constitute the activity of the animal; the more numerous and frequent they are, the more active is the life and the higher the rank of the living being in the scale of life. The degree of correspondence between the living thing and its environment is also its degree of life, inasmuch as in effect it connotes an increase in the number and in the mutual dependence of the vital changes which constitute life. A perfect correspondence would imply a perfect life. If to all changes of the environment there were opposed, as a counterbalance, changes in the living thing, natural death would be no more, nor death by disease or by accident, all of which are signs of a lack of correspondence.[1]
A definition of life which possesses these characters, and which expresses in a general formula the law of the changes of structure, and of the changes of function accompanying them; that is to say, which expresses the heterogeneity, the coördination, and the ever-increasing mutual dependence of these changes; and which at the same time expresses the ever-increasing correspondence which attaches them to the changes of the environment by an operation of equilibration—such a definition makes life to be an evolution, a succession of states of unstable equilibrium tending to perfect equilibrium; not
- ↑ We must here point out an erroneous statement made by Claude Bernard. In his article on the "Definition of Life" (Revue des Deux Mondes, 15 Mai, 1875, p. 345), this eminent physiologist offers as a complete definition of life a portion of Spencer's definition, as found in the "Principles of Biology." "The following definition," says he, "is proposed by Herbert Spencer: 'Life is the definite combination of heterogeneous changes, both simultaneous and successive.'" And he goes on to say: "Under this abstract form the English philosopher would specially indicate the idea of evolution and of succession observed in vital phenomena." If M. Claude Bernard had made this quotation from the "Principles of Biology" itself, he would have read immediately after this passage the following words: "This is a formula which fails to call up an adequate conception. And it fails from omitting the most distinctive peculiarity—the peculiarity of which we have the most familiar experience, and with which our notion of life is, more than with any other, associated. It remains now to supplement the definition by the addition of this peculiarity" (p. 71). Those who have studied Mr. Spencer's writings know how cautiously he sets about making a definition. He completes a formula, first expressed in very general terms, by the successive addition of essential characters, and for each of these characters he makes a minute analysis. Thus, having given as a preliminary result the formula quoted by M. Claude Bernard, Mr. Spencer adds that it needs to be completed, and a few pages further on (p. 74) he adds these words: "In correspondence with external coexistences and sequences." Again (p. 80), he writes: "The broadest and most complete definition of life will be—The continuous adjustment of internal relations to external relations." It is evident that M. Claude Bernard did not derive from the "Principles of Biology" the definition he quotes, and which he condemns. But ought he not to have taken it from that work?
