For, while the integration which accompanies growth tends in itself to set free mental power to work improvement, there is, both with increase of numbers and with increase in complexity of the social organization, a counter tendency set up to the production of a state of inequality, which wastes mental power, and, as it increases, brings improvement to a halt. To trace to its highest expression the law which thus operates to evolve with progress the force which stops progress, would be, it seems to me, to go far to the solution of a problem deeper than that of the genesis of the material universe--the problem of the genesis of evil. Let me content myself with pointing out the manner in which, as society develops, there arise tendencies which check development. There are two qualities of human nature which it will be well, however, to first call to mind. The one is the power of habit:--the tendency to continue to do things in the same way; the other is the possibility of mental and moral deterioration. The effect of the first in social development is to continue habits, customs, laws and methods, long after they have lost their original usefulness, and the effect of the other is to permit the growth of institutions and modes of thought from which the normal perceptions of men instinctively revolt. Now the growth and development of society not merely tend to make each more and more dependent upon all, and to lessen the influence of individuals, even over their own conditions, as compared with the influence of society; but the effect of association or integration is to give rise to a collective power which is distinguishable from the sum of individual powers. Analogies, or, perhaps, rather illustrations of the same law, may be found in all directions. As animal organisms increase in complexity, there arise, above the life and power of the parts, a life and power of the integrated whole; above the capability of involuntary movements, the capability of voluntary movements. The actions and impulses of bodies of men are, as has often been observed, different from those which, under the same circumstances, would be called forth in individuals. The fighting qualities of a regiment may be very different from those of the individual soldiers. But there is no need of illustrations. In our inquiries into the nature and rise of rent, we traced the very thing to which I allude. Where population is sparse, land has no value; just as men congregate together, the value of land appears and rises--a clearly distinguishable thing from the values produced by individual effort; a value which springs from association, which increases as association grows greater, and disappears as association is broken up. And the same thing is true of power in other forms than those generally expressed in terms of wealth.