70 MENTAL EVOLUTION IN xVNIMALS. 



CHAPTEK VI. 



Consciousness. 



Hitherto in this work I have been considering, as exclu- 

 sively as the nature of the subject permits, the physical or 

 objective aspect of mental processes, and of the antecedents 

 of these processes in the non-mental activities of living 

 organisms. It now devolves upon us to turn to the sub- 

 jective side of the matter, and still more closely, I may 

 observe, to the ejective side of it. That is to say, from this 

 point onward my endeavour will be to trace the probable 

 course of Mental Evolution by having regard to truly mental 

 phenomena, so far as these admit of analysis by subjective 

 or ejective methods. I desire, therefore, to draw promicent 

 attention to the fact that fram this point in my treatise I 

 take, as it were, a new departure ; for if this is not kept in 

 mind, my exposition may appear to resemble two separate 

 essays bound together rather than one continuous whole. In 

 my endeavour to draw a sharp line of demarcation between 

 the physiology and the psychology of my subject, I have 

 found it impossible to discuss the one without numerous 

 allusions to the other — the consequence being that hitherto, 

 while treating as exclusively as I could of the physiology of 

 vital processes, I have been obliged frequently to refer to the 

 psychology of mental processes, a knowledge concerning the 

 main facts of which I have taken for granted on the part of 

 any one who is likely to read this book. Thus it happens 

 that in now turning to investigate the psychology of these 

 processes, it is impossible to avoid a certain amount of over- 

 lapping with what has gone before. For example, in my 

 chapter on the Physical Basis of Mind, it was clearly impos- 

 sible not to allude to such leading principles of psychology 

 as sensation, perception, ideation, and others. Therefore, in 

 now undertaking an investigation of these various principles 



