This work, honoring Saul B. Sells, adds to the understanding of the science of psychology and the application of that knowledge to meaningful human endeavors. Covers topics including: the interactionist approach and the importance of multivariate design, accuracy of measurement in order to move toward the understanding of human behavior, and the necessity of understanding personality characteristics and environmental affect. Important reading for researchers, students, and professionals in all subdisciplines of psychology, including personality development, social psychology, research methods, evaluation and measurement.