Inventions and discoveries stand in serial relations along the lines of human progress, and register its successive stages; while social and civil institutions, in virtue of their connection with perpetual human wants, have been developed from a few primary germs of thought. They exhibit a similar register of progress. These institutions, inventions and discoveries have embodied and preserved the principal facts now remaining illustrative of this experience. When collated and compared they tend to show the unity of origin of mankind, the similarity of human wants in the same stage of advancement, and the uniformity of the operations of the human mind in similar conditions of society. Throughout the latter part of the period of savagery, and the entire period of barbarism, mankind in general were organized in gentes, phratries and tribes. These organizations prevailed throughout the entire ancient world upon all the continents, and were the instrumentalities by means of which ancient society was organized and held together. Their structure, and relations as members of an organic series, and the rights, privileges and obligations of the members of the gens, and of the members of the phratry and tribe, illustrate the growth of the idea of government in the human mind. The principal institutions of mankind originated in savagery, were developed in barbarism, and are maturing in civilization. In like manner, the family has passed through successive forms, and created great systems of consanguinity and affinity which have remained to the present time. These systems, which record the relationships existing in the family of the period, when each system respectively was formed, contain an instructive record of the experience of mankind while the family was advancing from the consanguine, through intermediate forms, to the monogamian. The idea of property has undergone a similar growth and development. Commencing at zero in savagery, the passion for the possession of property, as the representative of accumulated subsistence, has now become dominant over the human mind in civilized races. The four classes of facts above indicated, and which extend themselves in parallel lines along the pathways of human progress from savagery to civilization, form the principal subjects of discussion in this volume.