For some decades past we have been faced with a critical difficulty at the most critical and important point in the history of the earth. In the first place, it has been definitely established that in the earlier period of its history there was no life whatever--as the word is usually understood--upon the earth, as is abundantly shown elsewhere in this work. None of the conditions that make life possible, as we know it, were satisfied. As a recent French writer has said, life is an aquatic phenomenon, absolutely incapable of existence except in the presence of liquid water; and there was an age of vast duration in the history of the earth when all its water must have been in the gaseous state. Other reasons of equal cogency may be at present ignored. The broad fact is that, however widely students of this matter may differ on other points, there is absolute agreement upon the cardinal and initial fact that whereas there is life upon the earth now, there was a time when there was none. [Sidenote: A Gap in the Philosophy of Evolution] Now, in the ever memorable year 1859, Charles Darwin published a volume, the main thesis of which is now universally accepted, wherein the following is the last sentence: “There is grandeur in this view of life, with its several powers, having been originally breathed by the Creator into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being evolved.” “The Origin of Species” may be said, in a word, to establish the doctrine of the evolution of living organisms upon the earth “by laws acting around us”--to use Darwin’s own phrase. But Darwin’s work begins with and assumes the existence of life as an established planetary fact. There obviously remains a tremendous gap in the evolutionary philosophy as it stands in our statement of it thus far; and the first fact which we have to note is that the existence and recognition of this supposed gap, so far from being a matter of common recognition from the earliest times, so far from being an observation made by the critics of the doctrine of evolution, is, on the contrary, a special doctrine peculiar to scientific study and of quite recent origin, being indeed established--as was supposed--within the memory of many now living.