METHODS OF PHYSIOLOGICAL RESEARCH 41 



laws of the physical world are the laws according to which our 

 own psychical phenomena occur, because the physical world is 

 only our own idea. All science, therefore, is in this sense 

 psychology. 



We will now summarise our considerations regarding investiga- 

 tion. We started out with the question, whether there are 

 impassable limits to a knowledge of the world. If we understand 

 by knowledge the reduction of phenomena to the motions or the 

 mechanics of atoms, limits do, indeed, exist. For not only is the 

 atom, and hence matter, yet to be explained, but, as du Bois- 

 Reymond's clever undertaking has shown very clearly, it is 

 impossible to reduce psychical phenomena to the mechanics of 

 atoms. If, however, we conceive knowledge in a more general and 

 the only justified sense, namely, the reduction of phenomena to the 

 elements of reality, we find that no limits exist, for the sole reality 

 is our mind and all phenomena are only its contents ; explanation, 

 therefore, consists simply in the reduction of all psychical 

 phenomena to their elements. In this sense, all science, and in 

 general all knowledge, is in the end psychology. We thus come 

 to the only consistent standpoint, namely, monism, the unitary 

 view of the world, which seeks to derive all phenomena from a 

 single cause. From this standpoint we see whj' we meet with 

 limits when we define knowledge to be the reduction of phenomena 

 to the mechanics of atoms. An atom is not an element of reality 

 but a complex idea, hence all phenomena are not reducible to 

 atoms ; just as in a series of numbers the element of which is the 

 unit 1, all are reducible to the common unit but not to a number 

 more complicated than 1, e.g., 2. It is thus evident that a limit 

 can no more exist to the investigation of physical, than to that of 

 psychical phenomena ; for, since bodies, in other words, atoms or 

 matter, are only ideas, in other words, psychical phenomena, they 

 may be reduced to the same psychical elements as ideas. 



C. VITALISM 



We will now turn again to the consideration of vital phenomena. 

 The above reflections have shown the possibility of reducing all 

 phenomena, physical, as well as psychical, to a common cause. 

 The question that led to those reflections, whether vital phenomena 

 are based upon the same causes as those of non-living nature, 

 would be answered affirmatively if we were to go back to final 

 causes — and it has been found that no insurmountable boundaries 

 limit research. If, however, we confine ourselves to the special 

 field of physiology, the investigation of the physical phenomena of 

 life, we know that natural science has shown that the phenomena 



