"The final test of the value of what is called science is its applicability" are words quoted from the recent address of the President of the American Association for the Advancement of Science. With Huxley and President Woodward, I believe that there is no valid distinction between a pure science and an applied science. The practical needs of the astronomer to eliminate the personal equation from his observations led to the invention of the chronograph and the chronoscope. Without these two instruments, modern psychology and physiology could not possibly have achieved the results of the last fifty years. If Helmholtz had not made the chronograph an instrument of precision in physiology and psychology; if Fechner had not lifted a weight to determine the threshold of sensory discrimination, the field of scientific work represented to-day by clinical psychology could never have been developed. The pure and the applied sciences advance in a single front. What retards the progress of one, retards the progress of the other; what fosters one, fosters the other. But in the final analysis the progress of psychology, as of every other science, will be determined by the value and amount of its contributions to the advancement of the human race.
Here Witmer talks about how psychology can be used as a tool to help further humanity, much like tools that helped develop modern psychology. It's not just for science and knowledge that we use psychology, but to benefit the world.