Now, the remarkable fact--one of the most striking in the history of science--is that the time-honoured belief in spontaneous generation should have been attacked, and attacked with apparent success, just at the very time when it would otherwise have begun to assume real philosophic importance. For ages it had been accepted, taken as a matter of course, and not regarded as having any particular bearing upon the supreme questions. Then there came the time when this belief would have been an all-important link, without which the chain of evolution could not be completed, a link without which we were left to contemplate a perfect chain of inorganic evolution--the history of the earth before life--and a perfect chain of organic evolution--the history of life upon the earth, with an abyss between the two that could not be bridged, for how came life where there was no life? A series of experiments were made, experiments in which, strikingly enough, some of the greatest evolutionists of the day took a leading part, and these seemed to upset, just when it was most wanted by themselves for the establishment of their new doctrine, the belief which had gone without question for so many ages. [Sidenote: Is Life only Self-movement?] Now, some may be inclined to wonder how it should be that certain pioneers of the new doctrine of evolution, such as Tyndall and Huxley, should devote themselves with such persistence and labour and force to the overthrow of a doctrine which was so necessary for the complete establishment of their own case--so much so, that when they had overthrown it, they found themselves, as regards their own doctrine of evolution, placed in a difficulty from which they did not live to emerge. It is my own belief that this question can be answered, and the answer is of strict relevance to our present inquiry. I believe that Huxley and Tyndall were largely impelled by the desire to oppose a doctrine of the nature of life which was current in their time and is usually called “vitalism.” We shall not begin to understand the question of the beginning of life upon the earth, as that question may be legitimately stated to-day, unless we fully realise in what terms the doctrine of spontaneous generation was accepted in the past, and an understanding of this will teach us that the present-day revival of this doctrine presents it in a form very different from that which it so long held. Our discussion must be somewhat philosophic in character, but the question at issue is a highly philosophic one, and the reason why we have made so little progress in answering it hitherto is that men of science have too frequently discussed it without paying any serious attention to the profound philosophic questions which really underlie it. We have permitted ourselves to talk freely about life and matter, whilst claiming the right to take for granted the absolute validity of our conceptions of life and our conceptions of matter.