XV.] THE LAWS OF HABIT. 183 



is strengtheued by the converse facts which I have next 

 to state. 



As iust stated, great and sudden changes of circnm- Corre- 

 stances are destructive, and great and sudden changes ot changes in 

 habits are impossible. I believe we might say that great J^Jj^^^gYble. 

 and sudden changes of circumstances are destructive, 

 because great and sudden changes of habits are impossible.^ 

 And what confirms the belief that these two laws really 

 stand in the mutual relation of cause and effect is this 

 further pair of laws, which evidently are similarly related 

 to each other, — that great changes of circumstances are Great 



■ 1T1 J.1J 1 changes if 



often not destructive, provided they are not sudden ; and ^^^ sudden 

 that great changes of habit are often possible, provided are often 

 they are not sudden. I believe we may say, as before, that structive. 

 great and gradual changes of circumstances often are not gp^J^^j-jjg 

 destructive, Iccaiise great and gradual changes of habit are changes in 

 possible. I do not yet wish to speak of those changes which, possible.'' 

 as I believe, have occurred in geological time ; but, as an 

 instance of a wonderful change that has occurred in histo- 

 rical time, I may mention the dog, which, though naturally 

 carnivorous, has in his domestic state gradually become in 

 great part a vegetable feeder, and has been taught to tend 

 sheep. These changes must have taken many generations 

 to bring about. A carnivorous animal would perish if sud- 

 denly put on a vegetable diet : not that it would disagxee 

 with him — he would die of hunger sooner than touch it. 



The process of adaptation — or, in other words, the effects Adapta- 

 of changes of circumstances in producing new habitual cha- effected!''^ 

 racteristics— may now be stated ; not, indeed, in detail, but 

 with some degree of precision. External changes, if of any 

 importance, will either destroy the organism, or cause the 

 organism to acquire new habits, so as to adapt itself to the 

 changes. The new habits will be either active or passive. Active and 

 An animal may, for instance, be placed in a severer climate habits.'' 

 than that to which it is native : this may take place either 



1 Herbert Spencer would probably say, that if the organism, or the race 

 of organisms, is unable to readjust its internal relations to the new set of 

 external relations, it will perish. This would no doubt be true, but I do 

 not see that it would be in any sense an explanation. 



