There was a time [says Tyndall][66] when the earth was a red-hot molten globe, on which no life could exist.
Accordingly, as Professor Huxley acknowledges, spontaneous generation is an evolutionary necessity. Unless such generation can be shown to have taken place, or at the very least unless it can be shown to be naturally possible, the theory which requires it cannot be an established truth. But it is precisely as a scientifically established truth[{47}] that the doctrine of Evolution is presented to us, so firmly established indeed that we are warned "to doubt it is to doubt science."[67] It presents itself, moreover, as the most precious result of modern research, the appearance of which is as a sunrise illuminating the field of knowledge.[68]
This being so, and it being the first principle of Science that we should take nothing on faith and accept only what can be proved, it is our plain duty to satisfy ourselves, as scientific methods alone can rightly satisfy us, that a doctrine of such paramount importance is entitled to demand our acceptance.
What methods can claim to be scientific, all are agreed. Advances in science, Professor Tait warns us,[69]
come or not, as we remember or forget that our Science is to be based entirely upon experiment, or mathematical deduction from experiment.
Men of science [says Tyndall] prolong the method of nature from the present into the past. The observed uniformity of nature is their only guide.[70]
The man of science [says Huxley] has learned to believe in justification, not by faith, but by verification.[71]
In this manner must we test the Evolution theory, and spontaneous generation as an essential element[{48}] thereof. We will begin with Professor Huxley's statement of what he styles "the fundamental proposition of Evolution."[72]
That proposition is [he writes] that the whole world, living and not-living, is the result of the mutual interaction, according to definite laws, of the forces possessed by the molecules of which the primitive nebulosity of the universe was composed. If this be true, it is no less certain that the existing world lay, potentially, in the cosmic vapour; and that a sufficient intelligence could, from a knowledge of that vapour, have predicted, say the state of the Fauna of Britain in 1869[73] with as much certainty as one can say what will happen to the breath in a cold winter's day.
That is to say, the supposed nebula was a vast piece of mechanism, of unimaginable complexity, the component parts of which under the influence of such forces as gravitation, heat, chemical affinity, electricity and magnetism, have produced everything that has since appeared on earth, vegetable and animal life amongst the rest. How are we to assure ourselves that such was really the case?