You immediately infer that this skeleton once belonged to a living animal, that breathed, and fed, and walked about, exactly as animals do now. This conclusion seems so obvious and unavoidable, that we naturally conclude it to rest on the same foundation as the fact that the object is a skeleton, or that it was in the stone. But really it rests on a totally different foundation; it is a conclusion deduced by a process of reasoning from certain assumed premises.
Myriads, perhaps millions of skeletons of animals like this one have come at different times under human observation, which have been obviously referrible to creatures that, within the same sphere of observation, had been alive. No similar skeleton has ever come within the range of recorded observation that could be referred to any other source than that of a quondam living animal. On these premises you build the conclusion that a skeleton must, at some time or other, have belonged to a living animal. And it may seem an impregnable position; but yet its validity altogether depends on the exhaustive power of human observation. If I could show, to your satisfaction, that a skeleton might have existed; still more, if I could show you that a skeleton must have existed; still more, if I could prove that myriads of skeletons, precisely like this, must have existed, without ever having formed parts of antecedent living bodies; you would yourself acknowledge that your conclusions were untenable. The utmost you could affirm, would be, that possibly, perhaps probably, the skeleton you had found in the stone had at some time belonged to a living animal, but that, so far as any recognised premises exist, there was no certainty about it.
But the premises have not been fairly stated. There is more than the relation of precedence and sequence in what we know of the connexion between skeletons and living animals; there is the relation of cause and effect. It is not only that universal experience has declared the fact that every skeleton was once part of a living body; it has shown that the very structure and nature of the skeleton implied living body. The skeleton, in every part, displays a regard for the advantages of the living animal; it is built expressly for it; by itself it is nothing—a machine without any object; its joints, its cavities, its apophyses, its processes, all have special reference to tissues and organs which are not here now, but which belong to the living body.
And then experience has shown that the skeleton is made in a particular manner. The bone is deposited, atom by atom, in living organic cells, which are formed by living blood, which implies a living animal. The microscopic texture of your stone-girt skeleton does not differ from that of the skeleton which you cleaned from the muscles with your own hands; and therefore you infer that it was constructed in the same way, namely, by the blood of a living body.
Well, I come back, notwithstanding, to my position,—that your right to affirm this must altogether depend on the exhaustive power of that experience on which you build. And it will be overthrown, if I can show that skeletons have been made in some other way than by the agency of living blood.
Can I do this? I think I can. At least I think I can show enough greatly to diminish, if not altogether to destroy, the confidence with which you inferred the existence of vast periods of past time from geological phenomena. I can adduce a principle, having the universality (within its proper sphere) of law, hitherto unrecognised, whose tendency is to invalidate the testimony of your witness.