XVI] Sociological Application 305 



Measures may be taken to eliminate strains regarded as 

 unfit and undesirable elements in the population, or to 

 encourage the persistence of elements regarded as desirable. 

 From the standpoint of the sociologist these two kinds of 

 interference may seem merely complementary to each other, 

 but in the light of genetic physiology they are entirely 

 different. 



To the naturalist it Is evident that while the elimination 

 of the hopelessly unfit Is a reasonable and prudent policy 

 for society to adopt, any attempt to distinguish certain 

 strains as superior, and to give special encouragement to 

 them would probably fail to accomplish the object proposed, 

 and must certainly be unsafe. 



Comprehensive discussion of these questions would be 

 quite out of place here. It must suffice to point out that 

 the distinction is created partly by the fact that, whereas 

 our experience of what constitutes the extremes of unfitness 

 Is fairly reliable and definite, we have little to guide us In 

 estimating the qualities for which society has or may have 

 a use, or the numerical proportions In which they may be 

 required. But specially Important are the indications that 

 in the extreme cases, unfitness Is comparatively definite in 

 its genetic causation, and can, not unfrequently, be recognized 

 as due to the presence of a simple genetic factor. There is 

 as yet nothing In the descent of the higher mental qualities 

 to suggest that they follow any simple system of trans- 

 mission. It is likely that both they, and the more marked 

 developments of physical powers, result rather from the 

 coincidence of numerous factors than from the possession 

 of any one genetic element. 



Some serious physical and mental defects, almost certainly 

 also some morbid diatheses, and some of the forms of vice 

 and criminality could be eradicated if society so determined. 

 That however is the utmost length to which the authority 

 of physiological science can In the present state of know- 

 ledge be claimed for interference. ]\Iore extensive schemes 

 are already being advocated by writers who are neither 

 Utopians nor visionaries. Their proposals are directed in 

 the belief that society is more likely to accept a positive 

 plan for the encouragement of the fit than negative Inter- 

 ference for the restraint of the unfit. Genetic science, as I 



B. H. 20 



