SCIENCE. 



[N. S. Vol. XVI. No. 392. 



been successfully cai'ried through. For the 

 winter meetings we have further succeeded 

 in securing the cooperation of niunerous 

 national societies. The change in our time 

 of meeting is an experiment which we ven- 

 ture upon with the greater confidence, be- 

 cause of the success of our present meeting 

 in Pittsburgh. 



For my address this evening I have 

 chosen the theme: ' The Problem of Con- 

 sciousness in its Biological Aspects.' I hope 

 both to convince you that the time has 

 come to take up consciousness as a strictly 

 biological problem, and also to indicate the 

 nature of that problem, and some of the 

 actual opportunities for investigating it. 

 It is necessary to begin with a few words 

 on the philosophical interpretation. AVe 

 shall then describe the function of con- 

 sciousness in animal life, and consider its 

 part in the evolution of animals and of 

 man. The views to be stated suggest certain 

 practical recommendations, after present- 

 ing which I shall conclude by offering an 

 hypothesis of the relation of consciousness 

 to matter and force. 



Consciousness is at once the oldest prob- 

 lem of philosophy and one of the youngest 

 problems of science. The time is not yet 

 for giving a satisfactory definition of con- 

 sciousness, and we must fain content our- 

 selves with the decision of the metaphysi- 

 cian, who postulates consciousness as an 

 ultimate datum or concept of thought, mak- 

 ing the brief dictinn cogito, ergo sum the 

 pivot about which his system revolves. I 

 have endeavored vainly to discover by read- 

 ing and by questioning those philosophers 

 and psychologists whom I know, some deep- 

 er analysis of consciousness, if possible, 

 resolving it into something more ultimate. 



Opinions concerning consciousness are 

 many and often so diverse as to be mutually 

 exclusive, but they may be divided into two 

 principal classes. The first class includes 



all those views which make of consciousness 

 a real phenomenon ; the second, those views 

 which interpret it as an epiphenomenon. 

 We are, I think practically aU, agreed that 

 the fundamental question is: Does or does 

 not consciousness affect directly the course 

 of events? —or, stated in other words, is 

 consciousness a true cause? In short, we 

 encounter at the outset the problem of free- 

 will ; of which more later. . 



The opinion that consciousness is an 

 epiphenomenon has gained renewed prom- 

 inence in recent times, for it is, so to speak, 

 a collateral result of that great movement 

 of European thought which has culminated 

 in the development of the doctrine of mon- 

 ism. Monism itself is postulated chiefly 

 upon the two greatest discoveries of the 

 nineteenth century — the law of the conser- 

 vation of energy, and the law of the evolu- 

 tion of species. Both laws establish a 

 greater unity in the phenomena of the uni- 

 verse than mankind had previously been 

 able to accept. In the physical world, in- 

 stead of many forces, we now recognize 

 only one force, which assumes various 

 forms of energy; and in the living world 

 we recognize one life, which manifests it- 

 self in many types of form. With these 

 two unities in mind, what could be nearer 

 than the thought that the imity goes still 

 deeper, and that the phenomena of the in- 

 animate or physical, and of the living world 

 are fundamentally identical? The pro- 

 gress of physiological science has greatly 

 increased the impetus towards the adoption 

 of this thought as the cardinal dogma of 

 the new faith, because the work of phys- 

 iologists has been so devoted to the physical 

 and chemical phenomena of life, that the 

 conviction is widespread that all vital phe- 

 nomena are capable of a physical explana- 

 tion. Assuming that conviction to be cor- 

 rect, it is easy to draw the final conclusion 

 that the physical explanation suffices for 

 the entire universe. As to what is, or may 



