_Third._ Human speech seems to have been developed from the rudest and simplest forms of expression. Gesture or sign language, as intimated by Lucretius,[1] must have preceded articulate language, as thought preceded speech. The monosyllabical preceded the syllabical, as the latter did that of concrete words. Human intelligence, unconscious of design, evolved articulate language by utilizing the vocal sounds. This great subject, a department of knowledge by itself, does not fall within the scope of the present investigation. _Fourth._ With respect to the family, the stages of its growth are embodied in systems of consanguinity and affinity, and in usages relating to marriage, by means of which, collectively, the family can be definitely traced through several successive forms. _Fifth._ The growth of religious ideas is environed with such intrinsic difficulties that it may never receive a perfectly satisfactory exposition. Religion deals so largely with the imaginative and emotional nature, and consequently with such uncertain elements of knowledge, that all primitive religions are grotesque and to some extent unintelligible. This subject also falls without the plan of this work excepting as it may prompt incidental suggestions. _Sixth._ House architecture, which connects itself with the form of the family and the plan of domestic life, affords a tolerably complete illustration of progress from savagery to civilization. Its growth can be traced from the hut of the savage, through the communal houses of the barbarians, to the house of the single family of civilized nations, with all the successive links by which one extreme is connected with the other. This subject will be noticed incidentally. _Lastly._ The idea of property was slowly formed in the human mind, remaining nascent and feeble through immense periods of time. Springing into life in savagery, it required all the experience of this period and of the subsequent period of barbarism to develop the germ, and to prepare the human brain for the acceptance of its controlling influence. Its dominance as a passion over all other passions marks the commencement of civilization. It not only led mankind to overcome the obstacles which delayed civilization, but to establish political society on the basis of territory and of property. A critical knowledge of the evolution of the idea of property would embody, in some respects, the most remarkable portion of the mental history of mankind. It will be my object to present some evidence of human progress along these several lines, and through successive ethnical periods, as it is revealed by inventions and discoveries, and by the growth of the ideas of government, of the family, and of property.