220 Induction. [CHAP. IX. 



the question of vitality. Why do we reject any consideration 

 of these narrower classes ? We do reject them, but it is for 

 what may be termed a practical rather than a theoretical 

 reason. As was explained in the first chapters, it is essential 

 that our series should contain a considerable number of terms 

 if they are to be of any service to us. Now many of the 

 attributes of any individual are so rare that to take them 

 into account would be at variance with the fundamental 

 assumption of our science, viz. that we are properly concerned 

 only with the averages of large numbers. The more special 

 and minute our statistics the better, provided only that we 

 can get enough of them, and so make up the requisite large 

 number of instances. This is, however, impossible in many 

 cases. We are therefore obliged to neglect one attribute 

 after another, and so to enlarge the contents of our class ; at 

 the avowed risk of somewhat increased variety and unsuit- 

 ability in the members of it, for at each step of this kind we 

 diverge more and more from the sort of instances that we 

 really want. We continue to do so, until we no longer gain 

 more in quantity than we lose in quality. We finally take 

 our stand at the point where we first obtain statistics drawn 

 from a sufficiently large range of observation to secure the 

 requisite degree of stability and uniformity. 



20. In such an example as the one just mentioned, 

 where one of the successive classes man is a well-defined 

 natural kind or species, there is such a complete break in 

 each direction at this point, that every one is prompted to 

 take his stand here. On the one hand, no enquirer would 

 ever think of introducing any reference to the higher classes 

 with fewer attributes, such as animal or organized being: 

 and on the other hand, the inferior classes, created by our 

 taking notice of his employment or place of residence, &c., 

 do not as a rule differ sufficiently in their characteristics 



