NURTURE AND NATURE 5 



social reformer who without hesitation preach that 

 social salvation lies in this or that line of conduct ? 

 What must be our judgment of the ** practical man " 

 and the statesman who legislate in the direction indi- 

 cated by the falling scale of popular opinion, without 

 any real examination of the intense complexity, the 

 subtle biological effects of even slight changes, in the 

 factors on which our national weal depends ? 



A factory act may be carried owing to a wave 

 of popular emotion, which paints the horrors of 

 child-labour in the mills. Twenty years afterwards 

 it may become apparent that children were taken 

 care of because their labour was of value, but that 

 their value depending on their labour, they are, 

 since the act, an unmarketable commodity and have 

 ceased to be born on this very account^ 



What guide can we take to indicate the path of 

 true social reform through such a tangle of cause 

 and effect as we find involving the relative influence 

 of nature and nurture on human life ? It is not 

 enough to show that results are associated with this 

 or that factor; we have a vast complex of associated 

 factors, and out of this complex we have in some way 

 to pick out the more important and in a certain sense 

 the fundamental factors. The only effective method 

 by which at present it seems possible to approach such 

 a problem is that of correlation". Taking the social 



* For a fuller discussion of this point see Pearson : The Problem 

 of Practical Eugenics^ Eugenics Laboratory Lecture Series V. 



2 The coefficient of correlation measures the amount of resemblance 

 or association between characteristics of individuals or of things ; it is 

 represented by a decimal which lies between o and i. As the correlation 

 coefficient rises to i we approach a condition of absolute dependence. As 

 it falls to o we approach a condition of absolute independence. Thus 



