132 G. P. FRETS 



Quetelet (in the middle of the nineteenth century) was interested in 

 variability, i.e. the phenomena of variation, the small differences in nature. 

 (People, by the way, have continued to study this. It is said that when 

 Leibnitz, in a discourse, spoke about variability, the ladies in the audience 

 went into the park and sought for leaves which were alike and showed them 

 to Leibnitz.) 



Quetelet found that if, with regard to some characteristic or other, for 

 instance body length, one has a large number of examples at hand, and if 

 these can be grouped in a certain regular way, one has then to do with 

 material of the same sort. 



The curve of Quetelet demonstrates the distribution of the cases over 

 the various length-classes. The greatest number is in the middle of the 

 series of cases: it is the top of the curve. Left and right of the middle are 

 gradually decreasing numbers. The curve gives us in one glance an im- 

 pression of the distribution of the cases over the length-classes. The body- 

 length of the length-class with the greatest number is designated by Quetelet 

 as the mean length, "la moyenne." 



The regularity of the curve of the body-length, which is established by the 

 mutual regularity of the numbers of the various dimensions, is for Quetelet 

 the expression of the internal unity of mankind: they belong to one species. 

 And Quetelet ascribes this great significance to the curve, because, acccord- 

 ing to him, it agrees with the curve, which is demonstrated by the succession 

 of the co-efficients of the binomial formula of Newton. The frequency 

 curve approaches the ideal, i.e., the binomial curve. 



It is of great importance to make Quetelet's line of thought clear to us. 

 According to Quetelet the frequency curve shows that mankind is a unity. 

 The differences are unimportant; they arise as a result of the influence of the 

 environment. Quetelet called his average the type. Man forms a type. 

 The average is the important; the masses of the large numbers,— they 

 form the type. They characterize the nation to which they belong. 



Many have expressed their opinion about the large number of averages. 

 Nietzsche complains of the "many too many," Schopenhauer says that 

 there must be many millions of ordinary people that one genius may be 

 possible. 



To Quetelet the frequency curve is of almost mystical value. The study 

 of the statistics affects him. 



Another scholar who loves statistics, is Sir Francis Galton. With Galton 

 we come within the sphere of our subject : eugenics and education. Galton 

 was the originator of eugenics. His definition of this science "as the study 

 of the agencies under social control, which may improve or impair the racial 



