SECTION 22. OBSERVATION. 269 



should be completely separated from their kind from the time 

 of birth to full maturity, in order to resolve what is owing to 

 contact with others of their species, and what is not. This may 

 be afterwards varied by rearing members of one species with 

 members of another species, and by attempts at changing the 

 environment in diverse ways for the purpose of ascertaining 

 the adaptability of a species. The same class of experiment 

 might be resorted to for the purpose of ascertaining how far 

 the characteristics of the members of one race, nation, class, 

 or family, are due to heredity or environment. Here, of course, 

 where the experiment is restricted to the human species, it 

 needs to be understood that the child should be unaware that 

 it is adopted, and also that the foster parents should treat the 

 child as their own. In the case of man, the problem may be 

 also elucidated by indirect experiments, e.g., by studying the 

 adaptability to varied social conditions of adopted children and 

 the lives of individuals settled or educated abroad, and likewise 

 by examining the re-active influences of an exotic religion, as 

 of Islam in India, or tracing the social adaptability of the 

 members of the same quasi-race in various countries, as in the 

 history of the Jews, or inquiring into the effects of wholesale 

 immigration, as in the United States, on the mental characte- 

 ristics of the immigrants and their hosts. In any new sphere 

 simple observation, with and without instruments, should precede 

 experimental observation of a refined and quantitative nature, 

 and the value of the latter is comparatively small where, as 

 in the organic and cultural sciences, the issues are either com- 

 plicated or still in an inchoate state. Experiment is to instru- 

 mental observation what the latter is to unaided observation. 

 In varying an experiment of any kind, more especially Con- 

 clusions 27 and 28 should be applied. Finally, it should be 

 remembered that truly scientific experiments are rigidly quanti- 

 tative and strictly segregate individual facts and factors. 



132. (/n) Similarities. Observations should not slur over 

 any similarities, however different the accompanying circum- 

 stances and however unsuggestive at first the resemblances 

 seem. The discovery of the identity of the electric spark and 

 of the lightning is a case in point. 



Of course, all rational observation consists in grouping objects 

 according to their similarities; but for the very purpose of 

 disclosing resemblances we needs must, to begin with, strive 

 also to ascertain all the existing variations relative to our 

 enquiry. 1 



1 Darwin rightly expatiates on the importance of homologies : "What can 

 be more curious than that the hand of a man, formed for grasping, that of 

 a mole for digging, the leg of the horse, the paddle of the porpoise, and 

 the wing of the bat, should all be constructed on the same pattern, and 

 should include similar bones, in the same relative positions? How curious 

 it is, to give a subordinate though striking instance, that the hind-feet of 



