It is hardly necessary to discuss here the nature of the principle which thus shows its energy in the mind of man. Whether it is the cause or the effect of the refined organisation exhibited by the human body need not now be considered. If the latter, however, it may be objected that—assuming the human bodily organism to have been derived by descent from a lower animal form, according to the principles of natural selection—the intellectual faculty peculiar to man must have had analogous origin. To this it might be answered that man’s special faculty could not have been derived from an animal organism which does not itself possess it; but it is advisable rather to test that conclusion by a consideration of the physical data, and to see how far the argument for natural descent can be supported. According to this view, the tendency to the bipedal character was the first to become operative in the gradual development of man out of the ape. The erect form is supposed, however, to have been assumed that the arms and hands might have full play,[377] and it is evident that the free use of these would not have been of any special advantage without an increased brain-activity to guide them. Probably the changes required in the physical structure would be concomitant, but if they had a starting point it would surely be in the brain rather than in the extremities. The great development of the encephalon in man as compared with the monkey tribe would, in fact, require all the other supposed changes. Thus the greatly increased size and weight of the brain and its bony case, combined with the position of the foramen magnum at the base of the skull, would necessitate the erect position of the body, and this would supply the arms and upper part of the trunk with the required freedom of movement. These changes would be accompanied by the modification of the pelvis and lower limbs, while the increased sensitiveness of the skin, resulting from man’s more refined nervous structure, will sufficiently account for its general nakedness,[378] without supposing, with Mr. Darwin, the influence of sexual selection.[379] It is therefore in reality only the large size of the human brain that has to be accounted for, and this is by no means easy on the principle of natural selection. No doubt, with the increased activity of the mental powers, the brain would become more voluminous. But what was to determine that increased activity? It can only have been an improvement in the conditions of existence, to which man’s supposed ape progenitors were subjected, for which no sufficient reason can be given. Moreover, those progenitors would be subjected to the inevitable struggle for existence—a struggle which, even with man, in an uncivilised state, has a tendency to brutalise rather than to humanise. Under these conditions it would seem to be impossible for man to have raised himself to so great a superiority over his nearest allies as even the lowest savage exhibits.