74 BULLETIN OF THE 



this ; a philosophy which recognizes the validity of the mind's self- 

 consciousness as at least fully equal to the validity of its consciousness 

 of the conditions of the body by which it obtains a knowledge of the 

 external world. By this self-consciousness I know, with a certainty 

 which no doubt can ever disturb, that I have a mind; and by rightly 

 applying my reasoning powers to the data of my self-consciousness, 

 I can learn much that will be useful to me with regard to my 

 mental processes and the methods of employing them. But here I 

 have to stop. I can learn nothing, whether by consciousness or by 

 reasoning, with regard to the real nature of my conscious mind, 

 and however much it may long for immortality, neither philosophy 

 nor science afford any foundation of proof upon which it might 

 build its hopes. 



I have already said that I know mind only as a manifestation of 

 life. Its operations are intimately connected with the chemical and 

 physical phenomena of living beings, and it exercises over them a 

 certain directing influence, the nature of which we do not under- 

 stand. The obedience of our voluntary muscular actions to the 

 mandates of the guiding will is a familiar illustration of this 

 directing influence. On the other hand, all the knowledge of the 

 external world on which the mind exerts its reasoning power reaches 

 it through the organs of sense and the nervous system. Indeed, 

 our studies of the phenomena of sensation compel us to conclude 

 that what our mind really perceives, when it takes cognizance of 

 the external world, is merely the ever-changing panorama of our 

 own cerebral states. It should be anticipated, therefore, that dis- 

 turbed or morbid conditions of the brain would lead to irregular 

 or disorderly mental Operations; and the circumstance that this 

 really happens, affords no better proof of the materiality of thought 

 than is afforded by the circumstances of our ordinary normal 

 thought. 



So, too, since the cerebral changes, which the mind perceives, are 

 themselves of a purely chemico-physical nature, it should be 

 anticipated that, like the metabolic processes in other tissues, they 

 would be accompanied by an increased excretion of characteristic 

 waste-products, by evolution of heat and by afflux of blood. Ex- 

 perimental investigation has been directed to each of theSe points, 

 and some important observations have no doubt been made ; but 

 much of the testimony is conflicting, and our knowledge is still so 



