What means ‘to explain’? “To explain means simply to render clear that which is not clear or to reduce the unknown to the known, the complex to the simple (p. 104).... It is an indispensable presupposition of any natural science to consider nature as being capable of explanation (_erklärbar_), and this presupposition means that natural processes can be perfectly separated into most simple mechanical processes. This presumption can be realised to-day only on the basis of the atom-conception. It is accordingly not an experience, but a postulate of natural science to derive the whole material world-process from the mechanism of atoms. A description becomes an explanation in the measure in which it approaches this aim” (p. 105). The question is, whether in psychology, description can be supplanted by explanation, whether laws can be stated instead of mere rules. Professor Münsterberg takes that ground in psychology which as it appears to us is the only tenable ground, viz. that feelings are not motions and cannot be explained as converted physical processes. Professor Münsterberg says: “A sensation, a feeling, a will can never fill even the very smallest space. What is extended in space can never itself be a state of consciousness. To the psychologist this distinction is now a matter of course, so much so that it is difficult to call to one’s mind how much trouble it cost to acquire this insight. The object of psychology accordingly can never be an object in space, it can never be a process of motion, accordingly, even brain-irritation can under no circumstances ever become the object of psychology” (p. 97). Psychology has to investigate the psychical phenomena of the individual consciousness (p. 102), it has to separate it into its elements, i. e. those ingredients which are no longer divisible; which being done, psychology searches for the rules for the combinations of these psychical elements and shows us the different complex contents which are formed in this way by the elements up to that totality of single combinations which is given us as the contents of our spiritual personality (p. 103).