But all of these relations are in the realm of unreality. The atoms alone _are_: and yet the void, which ought _not_ to _be,_ in an unmistakable way _is_ also. To this mysterious vacuum which lies outside (and yet not outside) reality, to this not-being which _is,_ there can only be given a half-negative and baffling name. Let it be called Chance--or let it be called Necessity; let it be called inexplicable Law of co-existence and sequence,--the Force which is the beginning of motion. It is the ultimate key to the mystery--but it is at least a key which no human hand can use, or even lay hold of. It is enough for science if, leaving this ultimate inexplicability untouched, it trace in each separate instance the exact equation between the sum of the constituents and the total which they compose,--if it prove that the several items when put together exactly give the sum proposed. Identification--the establishment of quantitative equations--is the work of science. Identity is its canon, working on the presumption or axiom that there can be nothing in the result which was not in the antecedents or conditions. _Ex nihilo nihil fit._ The quantity of energy must always be the same, though its phases may vary, or temporarily avoid detection. Matter, i.e. the ultimate reality, is indestructible. In short, the method of analysis and synthesis, as that of addition and subtraction, is a calculus which takes the form of an equation.
So far the inorganic, inanimate world has been mainly in view. If we now turn to the organisms, we find the popular creed expressed in the adage _Omne vivum e vivo._ No eye has ever seen--though fanatical observers have sometimes so deluded themselves as to think they saw--a living being directly emerge from inorganic stuff. The saner student of physiology contents himself with leaving for the while the crux of the genesis of Life, and examining only the building up of the living creature out of its constituents. Here the atom is called the cell: every organism is a synthesis of cells, and in the cell we have the primary element of organic reality: _Omnis cellula e cellula,_ In the atom we have the ultimate element; in the cell a relative element,--the absolute beginning of a new order of things,--which we may, if we like, choose to treat (though only for logical simplicity's sake) as a gradual development from the other and more primitive, but which, so far as experience and history teach, is equally ultimate in its kind. But be the final constituent (physical) atom, or (physiological) cell, the relation of these constituents is at first conceived by science only as composition, or mechanical synthesis. It is only gradually that science begins to have doubts as to the inviolability and unalterableness of the elements. When the idea--not altogether new--of a 'latent meta-schematism' and latent process within the constituents is entertained and carried out in earnest, science has passed on to a new stage: from mechanical atomism to a dynamic and organic theory of existence. And the governing ideas of scientific logic have then ceased to be co-existence, and sequence, correlation and composition: the new category is intus-susception, development, adaptation not only external but internal.