“Given the existence of organic matter, given its tendencies to transmit its characteristics. Given, finally, the life conditions of the organic matter--these things in their totality are the causes of the present and past conditions of organic nature.” The greatness of this statement lies in its truly scientific exactitude, in its purely mechanistic apprehension of things. Just as the physicist, when he speaks of force and mass, intentionally eliminates everything of the actual--he simply cannot work until first all that is actual is eliminated, and pure relation-values established--so Darwin eliminates everything actual and sets to work with pure relation-values. Otherwise put: His teaching is nothing but a new system of measurement for actuality; and his greatness consists in this, that he was the first to take biology and apply to it the methods of the physicist. He it was who first approached the biological facts from the standpoint of differences of tension, differences of potentiality. His doctrine of the survival of the fittest is simply a kind of biological measure of force. What would one say of a man who made it a matter of reproach in connection with a yard-stick that it did not also at the same time indicate the nature and origin of the object measured by it? Only when it is independent of all such questions can anything serve as a standard of measurement. Where would the physicist find himself were he to say, “I will not concern myself with forces until I really know what force is?” He does not wish to know what force is. Were one to tell him he would stop his ears. He wants to make use of force, to be able to measure it; nothing more. In the same way Darwin does not in the least want to know and tell what living beings are. Should one say, “They are from God,” another, “They are from the devil,” he, Darwin, happens to be of the former opinion; but that has nothing to do with the problem before him. As the physicist lays hold of the pendulum in its swing and says, “If now I let it go, such and such phenomena must occur,” so Darwin--figuratively speaking of course--lays hold of the biological pendulum and says, “If now I let it go, this and this must happen.” The physicist so arranges his preliminary conditions that he can measure what occurs, and so also does Darwin. As the physical resultant is measured in the form of work, so Darwin measures the biological resultant in the form of the law of the survival of the fittest. Previous to him, biology stood much on the same level as the Ptolemaic universe which is based solely upon observation. Observation indeed permits of measurements of mass but not of measurements of force. At one bound Darwin leaps to an apprehension and treatment of biology strictly after the fashion of energetics, and thereby makes good his claim to rank with Robert Mayer and his successors. Comprehension, science, can only be carried on where there is flux, where there is change. It is the glory of the