Chap. III.] MORAL SENSE. 79 



for we are led by the hope of receiving good in return to 

 perform acts of sympathetic kindness to others ; and there 

 can be no doubt that the feeling of sympathy is much 

 strengthened by habit. In however complex a manner 

 this feeling may have originated, as it is one of high im- 

 portance to all those animals which aid and defend each 

 other, it will have been increased, through natural selec- 

 tion ; for those communities which included the greatest 

 number of the most sympathetic members, would nourish 

 best and rear the greatest number of offspring. 



In many cases it is impossible to decide whether cer- 

 tain social instincts have been acquired through natural 

 selection, or are the indirect result of other instincts and 

 faculties, such as sympathy, reason, experience, and a ten- 

 dency to imitation ; or again, whether they are simply the 

 result of lonor-continued habit. So remarkable an instinct 

 as the placing sentinels to warn the community of dan- 

 ger, can hardly have been the indirect result of any other 

 faculty ; it must therefore have been directly acquired. 

 On the other hand, the habit followed by the males of 

 some social animals, of defending the community and of 

 attacking their enemies or their prey in concert, may per- 

 haps have originated from mutual sympathy ; but courage, 

 and in most cases strength, must have been previously ac- 

 quired, probably through natural selection*. 



Of the various instincts and habits, some are much 

 stronger than others, that is, some either give more pleas- 

 ure in their performance and more distress in their preven- 

 tion than others ; or, which is probably quite as important, 

 they are more persistently followed through inheritance 

 without exciting any special feeling of pleasure or pain. 

 We are ourselves conscious that some habits are much 

 more difficult to cure or change than others. Hence a strug- 

 gle may often be observed in animals between different in- 

 stincts, or between an instinct and some habitual disposi- 



