a) _The original nature of man._--No one has stated more clearly than Thorndike that human nature is a product of two factors, (a) tendencies to response rooted in original nature and (b) the accumulated effects of the stimuli of the external and social environment. At birth man is a bundle of random tendencies to respond. Through experience, and by means of the mechanisms of habit and character, control is secured over instinctive reactions. In other words, the original nature of man is, as Comte said, an abstraction. It exists only in the psychic vacuum of antenatal life, or perhaps only in the potentiality of the germ plasm. The fact of observation is that the structure of the response is irrevocably changed in the process of reaction to the stimulus. The _Biography of a Baby_ gives a concrete picture of the development of the plastic infant in the environment of the social group. The three papers on differences between sexes, races, and individuals serve as an introduction into the problem of differentiating the aspects of behavior which are in _original nature_ from those that are _acquired_ through social experience. Are the apparent differences between men and women, white and colored, John and James, those which arise from differences in the germ plasm or from differences in education and in cultural contacts? The selections must not be taken as giving the final word upon the subject. At best they represent merely the conclusions reached by three investigators. Attempts to arrive at positive differences in favor either of original nature or of education are frequently made in the interest of preconceived opinion. The problem, as far as science is concerned, is to discover what limitations original nature places upon response to social copies, and the ways in which the inborn potentialities find expression or repression in differing types of social environment. b) _Human nature and social life._--Original nature is represented in human responses in so far as they are determined by the _innate structure of the individual organism_. The materials assembled under this head treat of inborn reactions as influenced, modified, and reconstructed by the _structure of the social organization_. The actual reorganization of human nature takes place in response to the folkways and mores, the traditions and conventions, of the group. So potentially fitted for social life is the natural man, however, so manifold are the expressions that the plastic original tendencies may take, that instinct is replaced by habit, precedent, personal taboo, and good form. This remade structure of human nature, this objective mind, as Hegel called it, is fixed and transmitted in the folkways and mores, social ritual, i.e., _Sittlichkeit_, to use the German word, and convention.