The human brain is the social organ; it is our medium of contact and exchange. Set a man in absolute solitude and his brain is affected at once. Cut off from the contact which enables it to freely receive and discharge its supply of social energy, its action becomes increasingly morbid. In proportion to the completeness and duration of the isolation the brain is injured, and ultimately ruined.
We know the effect of solitary imprisonment, or of being cast away alone on some remote island. Short of this we know the progressive effect of degrees of isolation. The lighthouse keeper knows—they put two men in lighthouses most removed from social touch; and even that is a dangerously “short circuit” for the social organ to act in. The solitary shepherd knows, on the wide waste plains of Australia or Texas. The hermit or recluse of any age, the separate dwellers in old houses in the country, any human creature who lives alone, is injuriously affected in brain action.
This is not saying that mere privacy is harmful—that is a necessity for the social brain; such temporary solitude as shall enable it to work out its special contribution to our common thought, and to rest from the forceful social currents. But however solitary the student or author, the product of his labour is for others, and must reach them; his brain must connect with the others, though at long range.
In this is another side of the proof of our mental collectivity. The poet feels for humanity, the student studies for humanity; the discoverer, inventor, all work for humanity. (This does not refer to the pay they expect, and their attitude toward it, but to the work itself.) All through our history we see the great-brained men who thought for the world, moved by a quenchless impulse to transmit this thought to the others, to pour out into the common stock the product of their brains. This they did because they must—even when loss and injury, ostracism or martyrdom followed. It is the compelling functional necessity of the brain to discharge into other brains, as well as to seek from them its vast and varied stimulus.
In more immediate and commonplace instances we see the same law. The difficulty of “keeping a secret,” i. e., of voluntarily retaining stimulus; the necessity of “relieving one’s mind”—a perfectly fit phrase, as much so as its familiar physiological analogue; the value of the confessional; and, commonest of all, the vivid interest of each human brain in the affairs of the others; all these show the collective nature of that organ.
The most ordinary woman, gossiping with her neighbours, manifests this social necessity for contact and exchange, however low. “Mind your own business!” we cry, and cry in vain. No brain advanced enough to be called human can possibly find full use and exercise in contemplation of one person’s business. It must concern itself in the business of the others, their common business.
The human brain is a social organ. Human thought is a social function.
Approach this fact along lines of evolution. The brain, like all other organs, is called for by conditions and developed by exercise. Simple conditions, simple exertions—low brain. Enlarge and elaborate the conditions—increase the exercises—and the brain develops. Observe here, within human history, how we have developed the brain of the dog by such change of condition and action.
In every form of animal life you find an exact relation between the range of activities of the creature and his degree of brain development. This is necessarily so, as the increase of activities is what produced that degree of development. The simple activities of the clam need no brain, and have none. The complex activities of the fox need a complex brain, and have it. Everywhere this exact proportion is found until you reach the human animal.
There is no relation whatever between the individual human being’s brain and his individual activities. But there is the same inexorable law of development by which alone to account for this highest of all brains, and the same relation is plainly to be seen between the social brain and its social activities. No conceivable activities of one biped, through however many generations, could have developed the brain of the architect, for instance. He has the power to think a church. He cannot build a church—never could—never could have even wanted one!