Next in logical order and in order of publication come the two volumes collectively entitled "The Principles of Psychology." In these volumes an attempt is made to trace objectively the evolution of mind from reflex action through instinct to reason, memory, feeling, and will, from the interaction of the nervous system with its environment. Subjectively, mental states are analyzed, and it is contended that all of them--including those primary scientific ideas, the perceptions of matter, motion, space, and time, assumed in the "First Principles"--can be analyzed into a primitive element of consciousness, something which can be defined only as analogous to a nervous shock. These perceptions have now become innate in the individual. They may be called--as Kant called space and time--forms of intuition; but they have been acquired empirically by the race, through the persistence of the corresponding phenomena in the environment, and from the accumulated experiences of each individual being transmitted in the form of modified structure to his descendants. This principle of heredity is one of the laws by which individuals are connected with one another into an organic whole; and we thus pass to what Spencer calls superorganic evolution, implying the co-ordinated actions of many individuals, and giving rise to the science of sociology. It is this science which Mr. Spencer undertakes to expound in the three volumes entitled the "Principles of Sociology." The first of these volumes presents a statement of the several sets of factors entering into social phenomena. These factors are, first, human ideas and feelings considered in their necessary order of evolution; secondly, surrounding natural conditions; and, thirdly, those ever-complicating conditions to which society itself gives origin. Under the caption "The Inductions of Sociology," are set forth the general facts, structural and functional, gathered from a survey of societies and their changes; in other words, the empirical generalizations that are arrived at by comparing different societies, or successive stages of the same societies. The author then examines the evolution of governments, general and local, as this is determined by natural causes; their several types and metamorphosis; their increasing complexity and specialization, and the progressive limitation of their functions. From political the author turns to ecclesiastical organization. He traces the differentiation of religious government from secular; its successive complications and the multiplication of sects; the growth and continued modification of religious ideas, as caused by advancing knowledge and changing moral character; and the gradual reconciliation of these ideas with the truths of abstract science. A good deal of space is devoted to what the author calls ceremonial organization, by which he means that third kind of government which, having a common root with the others,