The difficulty of the intellectual life is, that whilst it can never assume a position of hostility to religion, which it must always recognize as the greatest natural force for the amelioration of mankind, it is nevertheless compelled to enunciate truths which may happen to be in contradiction with dogmas received at this or that particular time. That you may not suspect me of a disposition to dwell continually on safe generalities and to avoid details out of timidity, let me mention two cases on which the intellectual and scientific find themselves at variance with the clergy. The clergy tell us that mankind descend from a single pair, and that in the earlier ages the human race attained a longevity counted not by decades but by centuries. Alexander Humboldt disbelieves the first of these propositions, Professor Owen disbelieves the second. Men of science generally are of the same opinion. Few men of science accept Adam and Eve, few accept Methuselah. Professor Owen argues that, since the oldest skeletons known have the same system of teething that we have, man can never have lived long enough to require nine sets of teeth. In regard to these, and a hundred other points on which science advances new views, the question which concerns us is how we are to maintain the integrity of the intellectual life. The danger is the loss of inward ingenuousness, the attempt to persuade ourselves that we believe opposite statements. If once we admit disingenuousness into the mind, the intellectual life is no longer serene and pure. The plain course for the preservation of our honesty, which is the basis of truly intellectual thinking, is to receive the truth, whether agreeable or the contrary, with all its train of consequences, however repulsive or discouraging. In attempting to reconcile scientific truth with the oldest traditions of humanity, there is but one serious danger, the loss of intellectual integrity. Of that possession modern society has little left to lose.