The demand for privacy and solitude becomes acute among people who do a great deal of mental work. "Man," says Nietzsche, "cannot think in a herd," and the thinker has traditionally been pictured as a solitary man. This is because quiet seems to be, for most men, an essential condition of really creative thought. There are some men who find it impossible to write when there is another person, even one of whom they are fond, in the same room. "No man," writes Mr. Graham Wallas, "is likely to produce creative thoughts (either consciously or subconsciously) if he is constantly interrupted by irregular noises." Constant association with other people means, moreover, continual distraction by conversation which seriously interrupts a consecutive train of thought. The insistence in public and college reading rooms on absolute quiet is a device for securing as nearly as may be privacy in intellectual work. Privacy is again demanded as a matter of emotional protection in individuals in whom there is a highly sensitive development of personal selfhood. We like to keep our concerns to ourselves, or to share them only with those with whom we have a marked community of interest and feeling. Children love to "have secrets they won't tell," and older people, especially sensitive and intelligent ones, feel a peculiar sense of irritation at having their personal affairs and feelings publicly displayed. Nearly everyone must recall occasions where he was vividly communicative and loquacious with a friend, only to relapse into a clam-like silence on the entry of a third person. This is primarily due to the fact that while men are by nature gregarious, their gregariousness early becomes specialized and aroused exclusively by people for whom they develop a sense of personal affection and common sympathy. Any intrusion from without this circle becomes an intrusion upon privacy. SATISFACTION IN PERSONAL POSSESSION: THE ACQUISITIVE INSTINCT. An almost universal human trait of considerable social consequence is the satisfaction men experience in having objects that are their own. Both animals and humans, apart from training, display a tendency to get and hold objects. This tendency may take extreme forms, as in the case of miserliness or kleptomania. It is evidenced in special ways in the collections that children, and some grown-ups, make of miscellaneous objects without any particular use, and with no particular aesthetic value. The objects which satisfy this instinct of possession may include material goods, family, or larger groups. In primitive tribes under the patriarchal system, the patriarch practically owns the tribe. Our laws not so long ago recognized the marriage relation as a state in which the wife is possessed or owned by the husband.