LIMITS OF OUR KNOWLEDGE OF NATURE. 27 



even by the Mind imagined by Laplace, if it made due use of its uni- 

 versal formula. 



Now, suppose we had such astronomical knowledge as this, with 

 regard to a muscle, a gland, an electrical organ, or a luminiferous or- 

 gan in the state of excitation; of a ciliary cell, a plant, an ovum in 

 contact with the sperm, or of a fruit at some stage of its development. 

 In that case we should possess the fullest possible knowledge of these 

 material systems, and our instinct of causality would be so far satisfied 

 that we should desire nothing more, save to know what matter and 

 force themselves are. Muscular contraction, secretion by the gland, 

 the shock of the electrical, and the shining of the luminiferous organ ; 

 ciliary action, growth and chemical action of the cell in the plant ; im- 

 pregnation and development of the e^g — all these phenomena, now 

 hopelessly obscure, would be as evident for us as the movements of 

 the planets. On the contrary, if we make a like supposition of astro- 

 nomical knowledge, with regard to the brain of man, or even the soul- 

 organ of the lowest animal, whose mental activity may be restricted 

 to the sensation of pleasure and pain, then, so far as all the material 

 phenomena are concerned, our knowledge would be as perfect, and our 

 instinct of causality as satisfied, as in the case of muscular contraction 

 or secretion, provided we had astronomical knowledge of muscles or 

 glands. The involuntary actions of the centres, and those not neces- 

 sarily connected with sensation — reflex action, simultaneous action, 

 respiratory movements, growth and decay of the brain and spinal 

 cord — would be completely understood. Further, those phenomena 

 which are always, and hence necessarily, simultaneous with mental 

 phenomena, would also be perfectly understood. And it certainly 

 were a great triumph of human knowledge if we were able to say that, 

 on occasion of a given mental phenomenon, a certain definite motion 

 of definite atoms would occur in certain definite ganglia and nerves. 

 It would be profoundly interesting if we could thus, with the mind's 

 eye, note the play of the brain-mechanism, in working out a problem 

 in arithmetic, after the manner of a calculating-machine ; or, even if 

 we could say what play of the carbon, hydrogen, nitrogen, oxygen, 

 phosphorus, and other atoms, corresponds to the pleasure we expe- 

 rience on hearing musical sounds ; what whirl of such atoms answers 

 to the climax of sensual enjoyment ; and what molecular storm to the 

 raging pain we feel when the trigeminus nerve is misused. The intel- 

 lectual enjoyment afforded by Fechner's preliminary studies in psycho- 

 physics, and by Donders's measurements of the duration of simpler 

 mental operations, gives reason to expect that such direct insight into 

 the material conditions of mental phenomena would be highly in- 

 structive. 



Still, as regards mental operations themselves, it is clear that, even 

 with astronomical knowledge of the mind-organ, they would be as un- 

 intelligible as they are now. Were we possessed of such knowledge, 



