According to John Stuart Mill, "It appears ... to be a condition of a genuinely scientific hypothesis, that it be not destined always to remain an hypothesis, but be of such a nature as to be either proved or disproved by that comparison with observed facts which is termed Verification." This statement is of value in confirming the general distrust of _mere_ hypothesis, and in distinguishing between the unverified and unverifiable presupposition and the legitimate assumption which through verification may become established doctrine. REFERENCES J. Cox, _Beyond the Atom_, 1913 (Cambridge Manuals of Science and Literature). R. K. Duncan, _The New Knowledge_, 1905. H. Poincaré, _Science and Hypothesis_. E. Rutherford, _Radioactive Substances and their Radiations_. F. Soddy, _The Interpretation of Radium_. F. Soddy, _Matter and Energy_ (Home University Library). Sir William A. Tilden, _Progress of Scientific Chemistry in our Own Time_, 1913. CHAPTER XIX THE SCIENTIFIC IMAGINATION Psychology, or the science of mental life as revealed in behavior, has been greatly indebted to physiologists and to students of medicine in general. Any attempt to catalogue the names of those who have approached the study of the mind from the direction of the natural sciences is liable to prove unsatisfactory, and a brief list is sure to entail many important omissions. The mention of Locke, Cheselden, Hartley, Cabanis, Young, Weber, Gall, Müller, Du Bois-Reymond, Bell, Magendie, Helmholtz, Darwin, Lotze, Ferrier, Goltz, Munk, Mosso, Maudsley, Carpenter, Galton, Hering, Clouston, James, Janet, Kraepelin, Flechsig, and Wundt will, however, serve to remind us of the richness of the contribution of the natural sciences to the so-called mental science. Indeed, physiology would be incomplete unless it took account of the functions of the sense organs, of the sensory and motor nerves, of the brain with its association areas, as well as the expression of the emotions, and the changes of function accompanying the development of the nervous system, from the formation of the embryo till physical dissolution, and from species of the simplest to those of the most complex organization.