fifiO THE PRINCIPLES OF SCIENCE. [CHAP 



and precise distinction between natural and artificial 

 systems. All arrangements which serve any purpose at 

 all must be more or less natural, because, if closely enough 

 scrutinised, they will involve more resemblances than 

 those whereby the class was defined. 



It is true that in the biological sciences there would be 

 one arrangement of plants or animals which would be 

 conspicuously instructive, and in a certain sense natural, 

 if it could be attained, and it is that after which natural- 

 ists have been in reality striving for nearly two centuries, 

 namely, that arrangement which would display the genea- 

 logical descent of every form from the original life germ. 

 Those morphological resemblances upon which the classi- 

 fication of living beings is almost always based are in- 

 herited resemblances, and it is evident that descendants 

 will usually resemble their parents and each other in a 

 great many points. 



I have said that a natural is distinguished from an 

 arbitrary or artificial system only in degree. It will be 

 found almost impossible to arrange objects according to 

 any circumstance without finding that some correlation of 

 other circumstances is thus made apparent. No arrangement 

 could seem more arbitrary than the common alphabetical 

 arrangement according to the initial letter of the name. 

 But we cannot scrutinise a list of names of persons without 

 noticing a predominance of Evans's and Jones's, under the 

 letters E and J, and of names beginning with Mac under 

 the letter M. The predominance is so great that we could 

 not attribute it to chance, and inquiry would of course 

 show that it arose from important facts concerning the 

 nationality of the persons. It would appear that the 

 Evans's and Jones's were of Welsh descent, and those 

 whose names bear the prefix Mac of Keltic descent. 

 With the nationality would be more or less strictly 

 correlated many peculiarities of physical constitution, 

 language, habits, or mental character. In other cases I 

 have been interested in noticing the empirical inferences 

 which are displayed in the most arbitrary arrangements. 

 If a large register of the names of ships be examined it 

 will often be found that a number of ships bearing the same 

 name were built about the same time, a correlation due to 

 the occurrence of some striking jncident shortly previous 



