94 Dependence of Mind upon natural causes. 



of impression. All purely mental acts appear to be 

 resolvable into these. 



Many persons still entertain the idea that mental 

 actions are largely independent of the natural condi- 

 tions to which physiological, chemical, and physical 

 phenomena are subject. The unscientific mind is 

 readily beguiled by easy schemes of mental action, or 

 simple systems of mental and moral philosophy, 

 unaware that great abstract truths often require deep 

 thought to discover them, or even to perceive them 

 when discovered and published. "A false notion, 



) which is clear and precise, will always meet a greater 

 number of adherents in the world than a true principle 

 which is obscure." It is not until unscientific persons 

 have become used to advanced scientific ideas and 

 nomenclature, and knowledge as so far progressed as 

 to enable thinking men to illustrate those ideas freely 



/ in familiar language, that great abstract truths are 

 believed by the public. The ordinary and simple 

 theory of the operations of the human mind is, that 

 they often arise without any cause, and are frequently 

 not obedient to ordinary influences, and this idea is 

 still entertained and promulgated even by some of 

 our most popular ministers of truth. It is therefore 

 necessary in order to further prove that new scientific 

 knowledge is really a basis of mental progress, to 

 point out a few of the chief ways in which mental 

 action essentially depends on scientific principles, and 

 to adduce a few instances in which other substances 

 than brain exhibit essentially similar phenomena. To 



