It can be based upon sexual desire; upon the instinct of property (wife and child as possessions); upon the instinct ofdominion, which constantly organises for itself the smallest form ofdominion, the family which requires children and heirs in order to hold fast, also in the physiological sense, to a certain quantum of acquired power, influence and wealth, so as to prepare for lasting tasks, and for solidarity in the instincts from one century to another.