An abiding faith in the importance of understanding the principles which govern human behavior underlies all psychological investigation and study. The study of personality, like the study of any other psychological discipline, is pursued with the thought that it will ultimately lead to the greater understanding of the forces that control human behavior.
In this textbook we shall attempt to gain insight into the meaning of personality and to gain an appreciation of the value of personality as an explanatory principle in human behavior. We shall do this by making a detailed study of the major methods used in the measurement of personality. If we can accept Lord Kelvin's dictum: that whatever exists can be measured, and if we can find a successful "measurer" of personality, we shall then surely know what personality is.
There are three objectives to be gained by the measurement of personality. They are the better understanding of individual behavior, the better understanding of group behavior, and the better understanding of the interactions between individual and group behavior. Traditionally, the first of these objectives belongs to psychology, the second to sociology, and the third to that hybrid discipline, social psychology. We shall not concern ourselves with this tripartite division, however, as it adds nothing of significance for our purposes. We shall be concerned in this volume with all useful methods of personality measurement; and unless it is necessary for our better understanding of them, we shall not concern ourselves with their academic origins.