I know all that may be urged against the theory of evolution.  In its favour are numerous proofs and most powerful arguments, which yet do not carry irresistible conviction.  We must beware of abandoning ourselves unreservedly to the prevailing truths of our time.  A hundred years hence, many chapters of a book instinct to-day with this truth, will appear as ancient as the philosophical writings of the eighteenth century seem to us now, full as they are of a too perfect and non-existing man, or as so many works of the seventeenth century, whose value is lessened by their conception of a harsh and narrow god.

Nevertheless, when it is impossible to know what the truth of a thing may be, it is well to accept the hypothesis that appeals the most urgently to the reason of men at the period when we happen to have come into the world.  The chances are that it will be false; but so long as we believe it to be true it will serve a useful purpose by restoring our courage and stimulating research in a new direction.  It might at the first glance seem wiser, perhaps, instead of advancing these ingenious suppositions, simply to say the profound truth, which is that we do not know.  But this truth could only be helpful were it written that we never shall know.  In the meanwhile it would induce a state of stagnation within us more pernicious than the most vexatious illusions.  We are so constituted that nothing takes us further or leads us higher than the leaps made by our errors.  In point of fact we owe the little we have learned to hypotheses that were always hazardous and often absurd, and, as a general rule, less discreet than they are to-day.  They were unwise, perhaps, but they kept alive the ardour for research.  To the traveller, shivering with cold, who reaches the human Hostelry, it matters little whether he by whose side he seats himself, he who has guarded the hearth, be blind or very old.  So long as the fire still burn that he has been watching, he has done as much as the best could have done.  Well for us if we can transmit this ardour, not as we received it, but added to by ourselves; and nothing will add to it more than this hypothesis of evolution, which goads us to question with an ever severer method and ever increasing zeal all that exists on the earth’s surface and in its entrails, in the depths of the sea and expanse of the sky.  Reject it, and what can we set up against it, what can we put in its place?  There is but the grand confession of scientific ignorance, aware of its knowing nothing—­but this is habitually sluggish, and calculated to discourage the curiosity more needful to man than wisdom—­or the hypothesis of the fixity of the species and of divine creation, which is. less demonstrable than the other, banishes for all time the living elements of the problem, and explains nothing.

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