THE WONDERS OF LIFE 



The two knowable attributes or inalienable properties 

 of substance, without which it is unthinkable, were de- 

 scribed by Spinoza as extension and thought; we speak 

 of them as matter and force. The "extended" (or 

 space-occupying) is matter; and in Spinoza "thought" 

 does not mean a particular function of the human brain, 

 but energy in the broadest sense. While hylozoistic 

 monism conceives the human soul in this sense as a 

 special form of energy, the current dualism or vitalism 

 affirms, on the authority of Kant, that psychic and 

 physical forces are essentially different; that the former 

 belong to the immaterial and the latter to the material 

 world. The theory of psycho-physical parallelism, as 

 developed especially by Wundt (1892), gives a" very 

 sharp and definite expression to this dualism; it says 

 that "physical processes correspond to every psychic 

 phenomenon, but the two are completely indepen- 

 dent of each other and have no natural causal connec- 

 tion." 



This wide-spread dualism finds its chief support in the 

 difficulty of directly connecting the processes of sensa- 

 tion with those of movement ; and so the one is regarded 

 as a psychic and the other as a physical form of energy. 

 The conversion of the outer stimulus (waves of light, 

 sound, etc.) into an inner sensation (sight or hearing) is 

 regarded by monistic physiology as a conversion of 

 force, a transformation of photic or acoustic energy 

 into specific nerve-energy. The important theory of 

 the specific energy of the sensory nerves, as formulated 

 by Johannes Mtill^r, forms a bridge between the two 

 worlds. But the idea which these sensations evoke, 

 the central process in the thought-organ or phronema 

 that brings the impressions into consciousness, is gen- 

 erally regarded as an incomprehensible mystery. How- 

 ever, I have endeavored to prove, in the tenth chapter 

 of the Riddle, that consciousness itself is only a special 



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