i8 4 THE POPULAR SCIENCE MONTHLY. 



Here we shall assume it to be an inevitable inference from the 

 doctrine of organic evolution, that the highest type of living 

 being, no less than all lower types, must go on molding itself to 

 those requirements which circumstances impose. And we shall, 

 by implication, assume that moral changes are among the changes 

 thus wrought out. 



The fact that when surfeit of a favorite food has caused sick- 

 ness, there is apt to follow an aversion to that food, shows how, 

 in the region of the sensations, experiences establish associations 

 which influence conduct. And the fact that the house in which a 

 wife or child died, or in which a long illness was suffered, be- 

 comes so associated with painful states of mind as to be shunned, 

 sufficiently illustrates, in the emotional region, the mode in which 

 actions may be determined by mental connections formed in the 

 course of life. When the circumstances of a species make certain 

 relations between conduct and consequence habitual, the appro- 

 priately-linked feelings may come to characterize the species. 

 Either inheritances of modifications produced by habit, or more 

 numerous survivals of individuals having nervous structures 

 which have varied in fit ways, gradually form guiding tenden- 

 cies, prompting appropriate behavior and deterring from inap- 

 propriate. The contrast between fearless birds found on islands 

 never before visited by man, and the birds around us, which show 

 fear of man immediately they are out of the nest, exemplifies 

 such adaptations. 



By virtue of this process there have been produced to some ex- 

 tent among lower creatures, and there are being further produced 

 in man, the sentiments appropriate to social life. Aggressive ac- 

 tions, while they are habitually injurious to the group in which 

 they occur, are not unfrequently injurious to the individuals 

 committing them ; since, though certain pleasures may be gained 

 by them, they often entail pains greater than the pleasures. Con- 

 versely, conduct restrained within the required limits, calling out 

 no antagonistic passions, favors harmonious co-operation, profits 

 the group, and, by implication, profits the average of its indi- 

 viduals. Consequently, there results, other things equal, a tend- 

 ency for groups formed of members having this adaptation of 

 nature, to survive and spread. 



Among the social sentiments thus evolved, one of chief impor- 

 tance is the sentiment of justice. Let us now consider more 

 closely its nature. 



Stop an animal's nostrils, and it makes frantic efforts to free 

 its head. Tie its limbs together, and its struggles to get them at 

 liberty are violent. Chain it by the neck or leg, and it is some 

 time before it ceases its attempts to escape. Put it in a cage, and 



