A change in family associations implies a corresponding change of vast importance in the intimate structure of society itself, in the social tissue. The state may make a marriage law, but it cannot create or modify the family tie beyond certain narrow limits. It can bestow privileges upon some one kind of association, but it cannot originate it, cannot enforce fidelity and chastity. The social tissue is its own end, or depends upon the whole system of instincts possessed by man as a social and rational creature. The development of society as an organic structure implies the development of customs in the race, and habits in the individuals forming it. There must be certain rules of conduct which are observed by all, in order that corresponding rules may be observed by each. Custom in the civilized society may be distinguished from positive law. In primitive states, the distinction is imperceptible. The authority of law itself must rest upon custom,--the custom of obedience. But physical force alone, or the dread of its application, cannot produce obedience; the application of such force is so little essential that a state of society is conceivable, in which it should disappear altogether; men might be willing to obey their rulers simply from respect and affection. The power of applying coercion in case of need must no doubt increase as the strength of the social bond increases; but that bond is also the stronger, in proportion as the need of applying it becomes less. The whole social structure, then, must rest, in the last resort, upon the existence of certain organic customs, which cannot be explained from without. They depend, for their force and vitality, upon the instincts of the individual as modified by the social factor; they correspond to a given state of the social tissue. A legal sanction may be added to any custom whatever, and thus it may seem that a state can make its own constitution and define its own organic laws; in reality, however, the power of making a certain constitution presupposes a readiness to act together and accept certain rules as binding, and thus implies a whole set of established customs, essential to the life of the society and giving rise to special types of character in its members. Every law of conduct more or less affects the character of the persons subject to it, so long as it is enforced; and necessarily, every variation in the character more or less affects the sentiments from which the external law derives its force. The correspondence, however, is not so intimate that one mode of statement can always be rendered into the other. For laws, indeed elaborate codes, are developed without seriously affecting the general character of the underlying customs, and in the same way instincts may vary widely without producing any normal change in the external order, though they affect the mode in which it works. The essence of any law is in the mutual pressure of the different parts of the social structure.