This conclusion is of great importance in the history of modern thought, and it was proclaimed with much rejoicing and vigour as a great achievement of science, whilst some of its chief advocates seemed at times to forget the extreme awkwardness of the inferences which had to be made from it. The doctrine may be stated in Latin in the form of the familiar dogma, “Omne vivum ex vivo,” every living thing from a living thing. Just as the existence of a man is quite sufficient to prove to us the prior existence of living human parents, just as we feel sure that every beast of the field has had living parents and that every oak has sprung from an acorn developed in a previous oak, so, according to the doctrine of “Omne vivum ex vivo,” we must believe that every living creature, whether human, animal, or vegetable, whether as big as the mammoth or as small as the smallest microbe not one-twenty-thousandth part of an inch in diameter, has sprung from living parents. Nature, according to this doctrine, was divided--as Nature, being a mighty whole, can never be divided--into two absolute categories, the living and the lifeless, or living matter and dead matter. Dead matter was notoriously dead and impotent, and life could not conceivably arise in it, though it could be used by life for purposes of food. On the other hand, living matter rejoiced in the possession of all those great attributes which lifeless matter lacked, and, in accordance with the contrast between the two kinds of matter, the living could never be produced from the lifeless but only from the living: for every creature, microbe or mammoth or man, we must trace back in imagination a series of living ancestors, differing perhaps in various characters, but always living. This series must be traced back and back and back until----? [Sidenote: Life Evolved from the Lifeless] And there the difficulty arose. For the uninhabitableness of the primitive earth was a fact of which men of science were as certain as if from some habitable planet they had been able to gaze upon it. Notwithstanding the dogma of “Omne vivum ex vivo,” it was impossible to assert that every living creature has an _endless_ series of ancestors. How, then, did life begin? What we may call the doctrine of the older orthodoxy--the doctrine of special creation, of supernatural interposition for the introduction of a new entity into the scheme of things--offered one alternative. To accept it, however, would be to abandon the whole modern conception of natural law and of a universe which was not created once on a day, and has not been tinkered with subsequently, but from everlasting to everlasting is the continuous expression to us of the Infinite and Eternal Power which to some eyes it veils and to others it reveals. Unless we are to abandon our philosophy, this alternative cannot be accepted, and it is now accepted by no philosophic thinker. [Illustration: BUFFON PLATO LAMARCK BERTHELOT HERSCHEL CLERK MAXWELL