ABSTRACT
In the present age, psychology is the most important, as it is the most difficult, of the sciences. It is the most important because it is the only science directly concerned to study and to interpret or explain the conduct of men; and in the present age, when the natural sciences have radically transformed our environment and have made it very much more complex, both physically and socially, than the environment of any former age, we are in danger of individual and social disaster through lack of such understanding as psychology seeks. For only through understanding the conduct of ourselves and of others can we hope to regulate it satisfactorily, to adjust it successfully to the many novel and constantly changing circumstances of our lives. Under the simpler conditions of former ages, conduct was regulated in the main by traditions and ancient customs which no man ventured to dispute or to defy. Traditions and customs are no longer adequate to the complexities of the modern world: the spirit of inquiry has challenged their authority and, in so doing, has robbed them of their power to control our conduct. Whether we like it or not, we are forced to ascend to the plane of rational regulation; and Reason, however powerful, can guide us aright only in the light of knowledge, knowledge of the nature of man, of the springs of his conduct, of the nature and sources of his knowledge, of the process of reasoning itself, its defects, its liabilities to error, to bias, to excess and defect.
