189G.] on Ludwig and Modern Phi/siology. 16 



suppose that tliere are two material Universes, one to wliicli the 

 material of our bodies belongs, the other comprising everything that 

 is not either plant or animal. 



The second reason is a practical one. We should have to go back 

 to the time which I have ventured to call prescientific, when the 

 world of life and organisation was supposed to be governed ex- 

 clusively by its own Laws. The work of the past fifty years has been 

 done on the opposite principle, and has brought light and clearness 

 where there was before obscurity and confusion. All this progress 

 we should have to repudiate, but this would not be all. We should 

 have to forego the prospect of future advance. Whereas by holding 

 on our present course, gradually proceeding from the more simple to 

 the more complex, from the physical to the vital, we may confidently 

 look forward to extending our knowledge considerably beyond its 

 present limits. 



A no less brilliant writer than the one already referred to, who is 

 also no longer with us, asserted that mind was a secretion of the brain 

 in the same sense that bile is a secretion of the liver, or urine that of 

 the kidney ; and many people have imagined this to be the necessary 

 outcome of a too mechanical way of looking at vital phenomena, and 

 that Physiologists, by a habit of adhering strictly to their own 

 method, have failed to see that the organism presents j^roblems to 

 which this method is not applicable, such e.g. as the origin of the 

 organism itself, or the origin and development in it of the mental 

 faculty. The answer to this suggestion is that these questions are 

 approached by Physiologists only in so far as they are ai)proacliable. 

 We are well aware that our business is with the unknown knowable, 

 not with the transcendental. 



During the last twenty years there has been a considerable 

 forward movement in Physiology in the psychological direction, 

 partly dependent on discoveries as to the localisation of the higher 

 functions of the nervous system, partly on the application of methods 

 of measurement to the concomitant phenomena of psychical processes. 

 And these researches have brought us to the very edge of a region 

 which cannot be explored by our methods — where measurements of 

 time or of sj^ace are no longer possible. In approaching this limit, 

 the Physiologist is liable to fall into two mistakes — on the one hand 

 that of passing into the transcendental without knowing it ; on the 

 other, that of assuming that what he does not know is not knowledge. 

 The former of these risks seems to me of little moment ; first, because 

 the limits of natural knowledge in the psychological direction have 

 been well defined by the best writers, as e.g. by du Bois-Eeymond in 

 his well-known essay " On the Limits of Natural Knowledge," * but 

 chiefly because the investigator who knows what he is about is 

 arrested in limine by the impossibility of applying the experimental 



Ucbcr die Grenzeu des Natureikeunens.' Rcden, Leipzig, 188G. 



