Large mental capacity in the individual, as we have already seen, has the effect of providing a wide freedom of response to instinctive impulses, so that, while the individual is no less impelled by instinct than a more primitive type, the manifestations of these impulses in his conduct are very varied, and his conduct loses the appearance of a {121} narrow concentration on its instinctive object. It needs only to pursue this reasoning to a further stage to reach the conclusion that mental capacity, while in no way limiting the impulsive power of instinct, may, by providing an infinite number of channels into which the impulse is free to flow, actually prevent the impulse from attaining the goal of its normal object. In the ascetic the sex instinct is defeated, in the martyr that of self-preservation, not because these instincts have been abolished, but because the activity of the mind has found new channels for them to flow in. As might be expected, the much more labile herd instinct has been still more subject to this deflection and dissipation without its potential impulsive strength being in any way impaired. It is this process which has enabled primitive psychology so largely to ignore the fact that man still is, as much as ever, endowed with a heritage of instinct and incessantly subject to its influence. Man’s mental capacity, again, has enabled him as a species to flourish enormously, and thereby to increase to a prodigious extent the size of the unit in which the individual is merged. The nation, if the term be used to describe every organization under a completely independent, supreme government, must be regarded as the smallest unit on which natural selection now unrestrictedly acts. Between such units there is free competition, and the ultimate regulator of these relations is physical force. This statement needs the qualification that the delimitation between two given units may be much sharper than that between two others, so that in the first case the resort to force is likely to occur readily, while in the second case it will be brought about only by the very ultimate necessity. The tendency to the enlargement of the social unit has been going on with certain temporary relapses throughout human history. {122} Though repeatedly checked by the instability of the larger units, it has always resumed its activity, so that it should probably be regarded as a fundamental biological drift the existence of which is a factor which must always be taken into account in dealing with the structure of human society.