Primitive races are governed largely by customs, and not until a race has shown itself amenable to the influence of custom is it prepared to be governed by laws. Laws differ from customs in that they have a definite sanction, in other words are enforced by some official authority. The institutions and practices which make up the social environment may be the outcome of long-standing custom, like the system of trial by jury, for example; or they may be brought into existence by law, as, for instance, the admission of women to suffrage or the establishment of national prohibition. The avowed purpose of all human institutions is to promote the greatest good of the greatest number, in other words to provide the best social environment. =Some Important Social Forces.=—The basis of custom is habit. Customs, in other words, are habits which extend [Sidenote: Two important social forces: habit and imitation.] to the whole community and receive its approval. We do not always realize how great a part _habit_ plays in our daily lives.[6] Without it the day’s work could not be done. By habit we walk, eat, dress ourselves, and perform many other common acts. Just think how long it would take a novice to put the various parts of a watch together; but the watchmaker, being habituated to the task, can do it in an hour. The foundation of habit is _imitation_. One man does a thing successfully; others follow his lead; a habit develops and a general practice or custom may be the ultimate outcome. The influence of custom is usually conservative, for when a custom is once firmly established it does not easily give way. Take the custom of smoking tobacco, for example. Europeans found it in vogue among the Indians when they first came to America; they adopted it and have kept it up for more than four hundred years. Sometimes, however, the habit or custom is only of short duration, in which case we commonly call it a fashion. Fashions come and go. A century ago men used snuff and women powdered their hair; but these things have wholly passed out of fashion today. =The Course of Social Progress.=—Having considered the various social factors and forces (development, inheritance, environment, custom, and so on) we are now in a position to ask and to answer the following question: In accordance with what principle has human society developed? There was a time when even educated people imagined that such organizations as the state were planned in advance, that individuals merely came together in prehistoric days and agreed after calm deliberation to establish a civil government. That, of course, was an absurd idea. Today we realize that one step in social organization led gradually to another, that institutions were not created but evolved, that various social factors and forces exerted an influence upon their development, and that the strongest institutions survived while the weaker disappeared.