as sure as I can be of any thing, that I had a thought yesterday morning, which I took care neither to utter, nor to write down, but my conviction is an utterly unverifiable hypothesis. So that unverified, and even unverifiable, hypotheses may be great aids to the progress of knowledge—may have a right to be believed with a high degree of assurance. And, therefore, even if it be admitted that the evolution hypothesis is, in great measure, beyond the reach of verification, it by no means follows that it is not true, still less that it is not of the utmost value and importance.
There is evidence which is perfectly satisfactory to competent judges, that we have already learned the actual historical process by which one existing species—the horse—came into existence during the Tertiary epoch. The evidence, based on the analogy of known developmental facts, that a three-toed Hipparion form, which lived in the Miocene epoch, gave rise, by suppression of the phalanges of its rudimental toes and some other slight modifications, to the apparently one-toed later Tertiary horse, is as satisfactory to my mind as the evidence, based on the analogy of known structural facts, which leads me to have no doubt that the said extinct Hipparion had a simple stomach and a certain kind of heart. If those so-called "Baconian principles," which everybody talks about and nobody dreams of putting into practice, forbid us to draw the one conclusion, they forbid us to draw the other.
The alternative hypotheses are two: either the Deity manifested his power on this earth, in the course of the Miocene epoch, by making the two primitive ancestors of all the horses out of inorganic matter, or something more unlike a horse than a Hipparion changed into one. The latter hypothesis is gratuitous and absurd. The former is not in itself absurd; but, unless the early chapters of Genesis mean something contrary to what they appear to mean (and one never knows what exegetic ingenuity may make of the "original Hebrew"), it is shockingly heretical, and I hasten to disown it, lest, by some such secret connection as bound Goodwin Sands with Tenterden steeple, it should land me in the cruelties of Caligula, and lead me to violate the precepts of the sagest of physicians, by indulging in Heliogabalian gluttony.
But, if the horse really has arisen in this way, what imaginable ground can there be for the enormous and, in that case, highly "unBaconian" assumption that the deer, and the ox, and the pig, have arisen in any other way? And if there is—not perhaps the complete evidence that we happen to possess in the case of the horse—but still much better evidence than there is for the authenticity and genuineness of the books called by the name of Moses, that these animals have been produced by a similar method, why may not the hypothesis that they have so arisen take its rank among the probable conclusions of science? Even though it must, in candor, be admitted
