What reason [he asks] does Professor Huxley give in explanation of his supposition?... The only reason distinctly implied is because the physical and chemical conditions of the earth's surface were different in the past from what they are now. And yet, concerning the exact nature of their differences, or the degree in which the different sets of conditions would respectively favour the occurrence or arrest of an evolution of living matter, Professor Huxley cannot possess even the vaguest knowledge. He chooses to assume that the unknown conditions existing in the past were more favourable to _Archebiosis_ (life-evolution) than those now in operation. This, however, is an assumption which may be entirely opposed to the facts. It is thus hard to understand how Professor Huxley could profess to justify his expectations by verification, for that the above account of the matter is no-wise overstated we have his own acknowledgment:[81] Of the causes which have led to the origination of living matter, it may be said that we know absolutely nothing.... Science has no means to form an opinion on the commencement of life; we can only make conjectures without any scientific value. Such a witness as Huxley might well suffice, but the question is so important as to make it advisable to call some others, though only a few amongst many who testify to the same effect. Like his friend and ally Huxley, Professor Tyndall believed that spontaneous generation had once occurred, and denied that it occurs now. As to the former article of his creed he was even more pronounced in his materialism. We have already heard him proclaim that in matter is to be discerned the promise and potency of all terrestrial life. He likewise inclined to believe that not only life but consciousness is immanent everywhere, in the vegetable and mineral no less than in the animal world,[82] and that not merely life and consciousness, but: All our philosophy, all our poetry, all our science, and all our art--Plato, Shakespeare, Newton, and Raphael--are potential in the fires of the sun.[83] Beliefs such as these might be thought to imply that the genesis of life is a simple affair, but Tyndall was no less convinced than Huxley that, as things are, it cannot be obtained without antecedent life on which to draw. Having described the experiments devised to test the matter, he thus concludes:[84] Here, as in all other cases, the evidence in favour of spontaneous generation crumbles in the grasp of the competent enquirer.