ON THE STATISTICAL VIEW OP NATURE. 601 



gether of multitudes of cases, each of which is by no 

 means uniform with the others. . . . Much light may 

 be thrown on some of these questions by the consider- 

 ation of stability and instability. When the state of 

 things is such that an infinitely small variation of the 

 present state will alter only by an infinitely small 

 quantity the state at some future time, the condition 

 of the system, whether at rest or in motion, is said to be 

 stable; but when an infinitely small variation in the 

 present state may bring about a finite difference in the 

 state of the system in a finite time, the condition of the 

 system is said to be unstable. It is manifest that the 

 existence of unstable conditions renders impossible the 

 prediction of future events, if our knowledge of the 

 present*state is only approximate and not accurate. It 

 has been well pointed out by Prof. Balfour Stewart that 

 physical stability is the characteristic of those systems 

 from the contemplation of which determinists draw their 

 arguments, and physical instability that of those living 

 bodies, and moral instability l that of those developable 

 souls which furnish to consciousness the conviction of 

 free-will." 2 



1 There is an awkward misprint 

 in the first edition of ' The Life, ' 

 which is corrected in the second 

 edition. 



2 Clerk - Maxwell frequently re- 

 verts to this subject. In an article 

 on " Molecules," contributed to the 

 ninth edition of the 'Ency. Brit.' 

 (reprinted in ' Scientific Papers," 

 vol. ii. ), he contrasts historical and 

 statistical knowledge as follows (p. 

 373) : " The modern atomists have 

 adopted a method which is, I 

 believe, new in the department of 



mathematical physics, though it 

 has long been in use in the section 

 of statistics. When the working 

 members of Section F (of the Brit. 

 Assoc.) get hold of a report of the 

 census, or any other document con- 

 taining the numerical data of 

 economic and social science, they 

 begin by distributing the whole 

 population into groups according to 

 age, income-tax, education, religious 

 belief, or criminal convictions. The 

 number of individuals is far too 

 great to allow of their tracing the 



