In applying this principle, we realize that such a faculty as Conscientiousness must be near the very summit, and that propensities to theft and murder must belong to the base. That such propensities exist in many, we know, and it is an absurd optimism which would ignore such facts because they are abnormal. The world is full of human abnormality, because it is not yet above the juvenile age of its growth, which is the age of feebleness and folly, disease and crime. The imperfect organism of childhood is incapable of resisting either temptation or disease. The twenty-five millions destroyed by the black death, in the fourteenth century, and the countless millions destroyed by war in all centuries, including the present, show how little we have advanced beyond the spirit of savage life. The ferocity of nations is as much the product of their cerebral organization, as the ferocity of the tiger, and springs from the same region of the brain,--lying on the ridge of the temporal bone,--a region that delights in fierce destruction, and is large in all the carnivora. It would be contrary to the spirit of science to ignore the fact that man has an element of ferocity similar to that of the tiger, because in the fully developed man that fierce element is overruled by the higher powers and confined to the destruction of that which does not suffer. The unwillingness to recognize anything evil comes not from the spirit of science, but from the _a priori_ assumptions of sentimental theology, which presumes that it thoroughly comprehends the Deity (who is beyond all human comprehension), and, out of its imaginative ignorance, fabricates _a priori_ philosophies and doctrines that everything in man is good, or that everything in man is evil. Anthropology has not thus been evolved from _a priori_ speculation, but presents its systematic doctrines as generalizations of the facts and experiments which have been carefully acquired and studied through the last half-century. The facts and experiments are too numerous to be recorded and published now, and had no channel for publication when they occurred. Everything in the lower half of the brain has a tendency to evil, in proportion to its over-ruling power, and everything in the upper half operates in proportion to its elevation with that controlling influence against evil, which uplifts him toward angelic or divine superiority. The brain may be divided by a horizontal line from the center of the forehead into its coronal and basilar halves, and by a vertical line from the cavity of the ear, into its frontal and occipital halves.