pology, zoology, embryology, pathology, chemistry, mathematics, etc.; they are important factors in certain fine and industrial arts; they are the basis of one of the most important medical disciplines. Why should not a man be a 'visionologist' or 'sightonomer'? When President Hall gives us an original and unique book on adolescence, nothing is gained by attempting to assign it to one of the conventional sciences. The work of Dr. Galton appears to me to be particularly unified, but it does not belong to psychology, nor to any other science. Why not call him an opportunist, or a liberal unionist, or a Galtonist, or better still call him no name at all?
In objecting to an artificial limitation of the field of the psychologist, I by no means want to aggrandize his office or to let psychology eat up the other sciences. The student of psychology is limited by the capacity of the human mind and of his own particular mind; he can, on the average, cover a range about as large as that of the student of any other science. If he would gladly get, he would also gladly give. If he is an imperialist who would set his flag on every corner of the earth, he yet tears down no other flag and welcomes the invasion of his own territory by every science.
As I claim for psychology the freedom of the universe in its subject-matter, so I believe that every method of science can be used by the psychologist. The two great achievements of science have been the elaboration of the quantitative method on the one hand and of the genetic method on the other. The uniformity of nature and the rationality of things are here presented in their most convincing, or at all events most plausible form. It would be an irreparable limitation if either of these methods did not apply in psychology. In my opinion they not only do obtain but must obtain. The mental and the physical are so inextricably interfused that quantitative and genetic uniformities could not exist in the physical world if absent from consciousness. If our mental processes did not vary in number, if they did not have time, intensity and space relations, we should never have come to apply these categories in physics, chemistry or astronomy. I am not prepared to attempt to clear up the logical questions involved; when water is muddy it is often wise to wait for it to settle rather than to keep stirring it up.
Under the conditions of modern science nearly all observations are experiments and nearly all experiments are measurements. A sharp distinction is usually drawn between an experiment and an observation. Thus Wundt, following Mill and other logicians, defines an experiment as an observation connected with an intentional interference on the part of the observer in the rise and course of the phenomena observed. But it is as properly an experiment to alter the conditions of observation as to alter the course of the phenomena observed. If the astronomer
