METHODS OF PHYSIOLOGICAL RESEARCH 39 



the preceding considerations. It was found that the sole reality 

 that we are able to discover in the world is mind. The idea of the 

 physical world is only a product of the mind, and with the altera- 

 tion of an old sentence of the sensualists, it can be said : Nihil est 

 in unimrso, quod non antea fiterit in intdledu. But this idea is 

 not the whole of mind, for we have many mental constituents, 

 such as the simple sensations of pain and of pleasure, that are not 

 ideas of bodies. The task of psychology, i.e., the investigation of 

 mind, consists in the analysis of all mental constituents. By 

 investigating the contents of mind, by decomposing the higher 

 psychical phenomena, the more complex groups and series of ideas, 

 into their simple constituents, psychology arrives, finally, at the 

 most primitive psychical phenomena, the psychical elements, and in 

 the same degree discovers the laws of the arrangement of these 

 elements into the higher groups and series of ideas. Just as in 

 mathematics the endless variety of numbers is formed according 

 to laws out of the numerical unit, so psychology reduces the end- 

 less variety of psychical phenomena to their formation, according 

 to laws, out of the psychical elements. But the idea of matter, 

 or, better, of an atom, is not a psychical element, it is a great com- 

 plex of highly developed ideas. An atom is nothing but a thing 

 possessing all the properties of a body, such as hardness, impene- 

 trability, form, and extension, all of which presuppose very complex 

 psychical processes. The endeavour of natural science to reduce 

 the phenomena of the physical world to the mechanics of atoms is 

 justifiable ; it is an endeavour to derive the phenomena of large 

 bodies from the properties of their material parts. But the 

 attempt to reduce to the motions of atoms all psychical phenomena, 

 not only ideas of the physical world but others, such as simple sen- 

 sations, is precisely as absurd as the endeavour to reduce all 

 numbers in the numerical series to 2 instead of to the numerical unit, 

 for the complex notion of the atom is not a unit, not a psychical 

 element. Herein lies the fallacy of the problem, and hence, as 

 the history of human thought has shown so strikingly, all attempts 

 to explain the psychical by the physical must fail. 



The actual problem is precisely the reverse. It consists not in 

 explaining psychical by physical phenomena, but rather in reducing 

 to its psychical elements physical, like all other psychical, phenomena. 



In natural science the view is frequently met with, that 

 knowledge of the world falls into two sharply separated categories, 

 namely, metaphysics and science. Metaphysics is left to 

 philosophy, and science is limited to the investigation of the 

 physical world. But the fact is often overlooked or intentionally 

 neglected, that every process of knowledge, including scientific 

 knowledge, is merely a psychical event, that science also deals 

 with " metaphysics," as in accordance with an ancient and unfor- 

 tunate manner of expression it is customary to term it, and even 



