654 THE POPULAR SCIENCE MONTHLY. 



tricity, only about 100 feet per second. They have also established the 

 fact of a chemical or molecular change in the brain corresponding 

 with changes in mental states ; and with great probability, also, a 

 quantitative relation between these corresponding changes, and thei'e- 

 fore a relation between them of cause and effect. In the near future 

 we may do more : we may localize all the faculties and powers of the 

 mind in different parts of the brain, each in its several place, and thus 

 lay the foundations of a scientific phrenology. In the far-distant 

 future we may do even much more : we may possibly connect every 

 diiFerent kind of mental state with a different and distinctive kind of 

 molecular or chemical change in the brain ; we may find, for example, 

 that a right-handed rotation of atoms is associated with love, and a 

 left-handed rotation with hate. We may do all this, and much more. 

 We may push our knowledge in this direction as far as the boldest 

 imagination can reach, and even then we are no nearer the solution 

 of this mystery than before. Even then it would be impossible for us 

 to understand how brain-changes can produce even the simplest psy- 

 {hological phenomena such as sensation, consciousness, xoill. By no 

 Tort of the mind can we conceive how molecular motion can pi-oduce 

 sensation or consciousness. The two sets of phenomena belong to 

 difi'erent orders orders so different, that it is simply impossible to 

 construe the one in terms of the other. 



It is not thus with other groups of phenomena in relation to one 

 another. The phenomena of motion, heat, gravity, light, electricity, 

 chemical afiinity yea, also of vitality have been, or may be, con- 

 strued in terms of each other, and all in terms of molecular motion. 

 Whether our present theories on this subject be true or not, may ad- 

 mit of doubt ; but a true theory is at least conceivable ; all these may 

 conceivably be reduced to the same order. But no amount of knowl- 

 edge nor strength of imagination will in the least degree help us to 

 understand the mysterious causal relation between the molecular 

 changes in the brain and the corresponding efiects in the mind, or 

 between changes in the mind and corresponding changes in the brain. 

 I wish to put this as clearly and as strongly as I can. Suppose, then, 

 an infinite human knowledge infinite in degree, but human in hind ; 

 suppose, in other words, an absolutely perfect science, such as was 

 conceived and admirably expressed by Laplace a science which had 

 completely subdued its whole domain and reduced it to the greatest 

 simplicity, so that the whole cosmos and its phenomena is expressed 

 by a single mathematical formula, which, worked out with positive 

 signs, would give every phenomenon which would ever occur in the 

 future, or with negative signs every event which had ever occurred 

 in the past. Even to such an infinitely perfect science the causal 

 relation of molecular motion on the one hand to sensation, conscious- 

 ness, thought, and emotion on the other, or vice versa, would still 

 be utterly unintelligible. Like the essential nature of matter, or 



