Of such a society as this it may indeed be said, that it "exists for the benefit of its members, not its members for the benefit of society. It has ever to be remembered that great as may be the efforts made for the prosperity of the body politic, yet the claims of the body politic are nothing in themselves, and become something only in so far as they embody the claims of its component individuals."[30] In other words, the social organism, as Spencer sees it, exists not for itself but for the benefit of the separate organs of which it is composed, whereas, in the case of biological organism the situation is reversed. There the parts manifestly exist for the whole and not the whole for the parts. Spencer explains this paradoxical conclusion by the reflection that in social organisms sentience is not localized as it is in biological organisms. This is, in fact, the cardinal difference between the two. There is no _social sensorium_. In the one (the individual), consciousness is concentrated in a small part of the aggregate. In the other (society), it is diffused throughout the aggregate: all the units possess the capacities for happiness and misery, if not in equal degrees, still in degrees that approximate. As then, there is no social sensorium, the welfare of the aggregate, considered apart from that of the units, is not an end to be sought. The society exists for the benefit of its members; not its members for the benefit of the society.[31] The point is that society, _as distinct from the individuals_ who compose it, has no apparatus for feeling pain or pleasure. There are no _social_ sensations. Perceptions and mental imagery are individual and not social phenomena. Society lives, so to speak, only in its separate organs or members, and each of these organs has its own brain and organ of control which gives it, among other things, the power of independent locomotion. This is what is meant when society is described as a collectivity. VI. SOCIAL CONTROL AND SCHOOLS OF THOUGHT The fundamental problem which Spencer's paradox raises is that of social control. How does a mere collection of individuals succeed in acting in a corporate and consistent way? How in the case of specific types of social group, for example an animal herd, a boys' gang, or a political party, does the group control its individual members; the whole dominate the parts? What are the specific _sociological_ differences between plant and animal communities and human society? What kind of differences are _sociological differences_, and what do we mean in general by the expression "sociological" anyway? Since Spencer's essay on the social organism was published in 1860,[32] this problem and these questions, in one form or another, have largely absorbed the theoretical interest of students of society. The attempts to answer them may be said to have created the existing schools into which sociologists are divided.