4. _The pressure of increase of numbers on resources is confined by individual industry and by private property to special portions of the population._ A condition of communism, where all the members of the tribe or family share equally, means that all enjoy together when food and wealth are abundant, and all starve together when it becomes scarce. Along with a fierce enmity for other tribes, is found in many early societies a close approximation to tribal communism. Private property alters the nature of the struggle for subsistence and of the motives for limiting population. Society divides into a number of partially independent classes or family groups, each holding its share of wealth apart, not in common with the tribe. A society with private property is like a ship divided into a number of water-tight compartments. In communistic conditions if population increases, all sink together into want. The self-interest of those having private property keeps them from dividing their property, and starvation is confined to the propertyless members. This acts in two ways: it increases the motive for the production of wealth; it gives a motive for the limitation of the consumers of the wealth. A smaller family with larger resources means a wider margin between numbers and misery. This converts the problem of population from a material one of a balance of food and physical needs, to a psychic one of a balance of motives in the minds of men. When this stage is reached, the extreme objective limit of the birth-rate or of increase of population is no longer attained in the well-to-do classes, although it may still continue to be in the less provident. [Sidenote: Social classes differ in volitional control] 5. _Volitional control is effective in very different degrees in different families and industrial classes._ The possession of property is both a sign of forethought and an incentive to it. Concern for the welfare of children is one of the most powerful motives, especially after social distinctions become marked. It may become abnormally strong, leading parents to sacrifice their own welfare or their own lives foolishly for their children, as is done often in the accumulation of property. Among the classes with property the provision for the children depends not only upon the amount of wealth, but upon the number among whom it is to be divided. It is simple division: wealth the dividend, number of children the divisor. Among the poorer classes very different motives operate. After the first few years the parents' income is increased by the earnings of the children, both on the farm and in the factory districts if the laws do not prohibit child labor. Moreover, when the children are grown, their wages will depend on the general labor market, not upon the number of their brothers and sisters. So, according as the family income is from rents or from wages, the motives of the parents differ. [Sidenote: Motives in volitional control]