THE CAUSATION OF DISEASE. 1 95 



namely, which impels to action; just as there is a great 

 distinction between, a government and the laws which it 

 enacts. The actions dictated by reason have not the fixed 

 and stereotyped character belonging to instinctive acts ; for a 

 reasoned act is not, like an instinctive one, the result of the 

 impulsive prompting of an inborn voice ; it is, on the contrary, 

 the result of a complex mental process, and this mental result 

 cannot possibly have come under the influence of natural 

 selection; wherefore we are at once led to expect reason to 

 be a less perfect guide than instinct. 



With the many imperfections of reason I shall presently deal, 

 but before doing so let me remark how important is that stage 

 in evolution when reason first appears in full force. Although 

 many of the brutes are endowed with reason, they are all tied 

 down by instinct to act more or less mechanically on a narrow 

 stereotyped plan. Man, on the other hand, is essentially a 

 reasoning being, guided only in a small degree by instinct ; so 

 that, as I have already said, we may more or less sharply 

 separate him from the brutes, in that he is governed by reason, 

 they by instinct. Now, prior to the evolution of reason, such 

 as we find it in man, we observe Nature at work in her more 

 simple physical aspect, life being a mere complex play of 

 chemico-physical force, and instinct (although in its higher 

 developments largely tinged with a mental element) essen- 

 tially a nervo-automatic process, the product, in a large 

 degree, like the body itself, of natural selection. But with the 

 evolution of reason, such as we find it in man, an entirely 

 different order of things obtains; for whether we regard 

 mind as necessarily linked with matter, or as something 

 quite distinct and separate from it, the fact remains that we 

 have in its higher creations something very different from 

 anything which has hitherto taken part in the operations of 

 nature* — a power, namely, which diverts the course of mere 



* There can be no doubt that the evolution of mind as it appears in man, 

 more especially in civilized man, marks an important epoch in the history of 

 evolution, for the reasons I have given in the above text, and in order to em- 

 phasize this fact — the fact, namely, that mind henceforth exercises an im- 

 portant influence over natural processes hitherto more or less independent of 

 it, and, secondly, that the process of natural selection in man is interfered 

 with — I have kept my text unaltered, but I can now see that neither of these 



