Few subjects have led to discussion so animated and prolonged as has the definition of the science of sociology. It is therefore necessary, as it is hoped that this essay may be capable of sociological applications, that the writer should define the sense in which he uses the term. By calling it a science is, of course, denoted the view that sociology is a body of knowledge derived from experience of its material and co-ordinated so that it shall be useful in forecasting and, if possible, directing the future behaviour of that material. This material is man in society of associated man. Sociology, therefore, is obviously but another name for psychology, in the widest sense, for, that is to say, a psychology which can include all the phenomena of the mind without the exception even of the most complex, and is essentially practical in a fuller sense than any orthodox psychology which has yet appeared. Sociology has, of course, often been described as social psychology and has been regarded as differing from ordinary psychology in being {12} concerned with those forms of mental activity which man displays in his social relations, the assumption being made that society brings to light a special series of mental aptitudes with which ordinary psychology, dealing as it does essentially with the individual, is not mainly concerned. It may be stated at once that it is a principal thesis of this essay that this attitude is a fallacious one, and has been responsible for the comparative sterility of the psychological method in sociology. The two fields—the social and the individual—are regarded here as absolutely continuous; all human psychology, it is contended, must be the psychology of associated man, since man as a solitary animal is unknown to us, and every individual must present the characteristic reactions of the social animal if such exist. The only difference between the two branches of the science lies in the fact that ordinary psychology makes no claim to be practical in the sense of conferring useful foresight; whereas sociology does profess to deal with the complex, unsimplified problems of ordinary life, ordinary life being, by a biological necessity, social life. If, therefore, sociology is to be defined as psychology, it would be better to call it practical or applied psychology than social psychology. The first effect of the complete acceptance of this point of view is to render very obvious the difficulty and immensity of the task of sociology; indeed, the possibility of such a science is sometimes denied. For example, at an early meeting of the Sociological Society, Professor Karl Pearson expressed the opinion that the birth of the science of sociology must await the obstetrical genius of some one man of the calibre of Darwin or Pasteur. At a later meeting Mr. H. G. Wells went farther, and maintained that as a science sociology not only does not but cannot exist. {13}