There result from all this two sorts of ideas in palæontology, the one positive, the other negative: it is true, however, that the latter diminish continually the profit we obtain from the former, and it is important to remember that this negative evidence is the only basis upon which rests the hypothesis that man is so new to our globe as some imagine. Every moment we may expect to see the interior of the earth prove the contrary. Instead of discoveries following one another, and being linked together as in other sciences, forming a whole which hangs together by itself, palæontology goes on from hand to mouth, as it were, at the caprice of whatever may happen, without knowing the wonder which is about to be revealed, perhaps at a few steps from a path which millions of men have passed by. It is very true that the human bones which have hitherto been found in the ground in caverns seem to proceed from a form but slightly different from our own; but all this is very recent, relatively to this _considerable time_ of which we have before spoken. Who can say but that we may find very soon a skull which must be classed, whether one will or not, between the anthropomorphous apes and man? Étienne Geoffroy, led by the logical nature of his ideas, naturally admitted this intermediary form, anterior to our own; but seeing the mammalia of the last geological ages generally larger than those which are contemporary with ourselves, he concluded besides that our immediate ancestors were giants, and that we have degenerated, like the descendants of the bears and hyenas found in caverns.[325] Nothing has appeared in order to justify this hypothesis, and everything seems to show that since that epoch the height of the genus _homo_ has not much altered, whilst the size of the different genera of ferines, ruminants, and pachyderms has positively varied. _Recapitulation._ Since we have found that man is comparable in all points to animals, we ought to seek for him and for them a common origin, and the difficulty of admitting an initial miracle has led us to the idea of _evolution_. If in the science of observation it is permitted to refer to general ideas, assuredly it is so in this case; philosophy commences where science ends, and it belongs to it to give us an explanation of the matter; but we must wait for the future for a true positive solution of the problem, perhaps from advanced geology, perhaps from experiments. The genius of man has no bounds, who can say to what it may reach? who knows whether, like a new Prometheus,[326] a creator in his turn, he may not one day breathe life into some new species, which will suddenly appear from his laboratories? CHAPTER IX. SYSTEM.