in the common heritage of modern science. The notable extension of knowledge through experiment is ever paralleled by a development of logical method and critical interpretation, as well as by an extension of technical resources. To this general movement psychology owes its present status, and shares in its benefits. It finds a concrete expression in the psychological laboratory, and a yet more comprehensive one in the transformation of the entire range of accredited problems, and the introduction of new realms of inquiry. The technical advance in the knowledge and control of physical, biological and psychological forces characterizes the modern world of science. These divisions of intellectual enterprise, though differently directed, are mutually corroborative. They progress by the application of a common logic. Standards of evidence, extension of data, and the basis of interpretation develop together. Jointly they determine the spirit of modern science, from which psychology along with the rest of the sciences, receives its directive bent and the temper of its pursuit. A coordinate factor is the dominance of an expanding practical philosophy—a worldly wisdom born of a larger experience in social, political and economic relations. It is expressed in the standards of intercourse and living, and more particularly in the cosmopolitan outlook, reflecting the insight into the determination of events and careers as of the qualities of men shaped by, and shaping them. This influence extends to literature, philosophy and the arts of life; it provides the background against which the technical pursuits are projected, from which they emerge.
The establishment of the principles and the body of knowledge determining the present study of character and temperament is the convergent product of a complex development; it forms an integral part of the general advance for which the nineteenth century—the culmination setting in with marked acceleration in the second half thereof—is notable. Our purpose will be served by considering broadly the contributory branches of investigation to which psychology is particularly indebted. Among these the establishment of the relation between body and mind is clearly central. Equally fundamental is the interpretation of the vital processes and provisions through a unifying and illuminating principle. This was supplied by the master-key of evolution, and at once rationalized and vitalized the conception of origins and transformations of natural processes and products—including the manifestations and endowments of the mental nature. Interpretation became possible in a convincing language—quieting the babel of tongues. Both of these guiding principles—the latter particularly—were revolutionary in their influence, not primarily by the new exten-
