INDISTINCTNESS OF IDEAS. 255 



with its stationary character. I shall point out 

 some indications of the intellectual peculiarity of 

 which I speak. 



1. Collections of Opinions. The fact, that mere 

 Collections of the opinions of physical philosophers 

 came to hold a prominent place in literature, already 

 indicated a tendency to an indistinct and wandering 

 apprehension of such opinions. I speak of such works 

 as Plutarch's five Books " on the Opinions of Philo- 

 sophers," or the physical opinions which Diogenes 

 Laertius gives in his "Lives of the Philosophers." 

 At an earlier period still, books of this kind appear ; 

 as for instance, a large portion of Pliny's Natural 

 History, a work which has very appropriately been 

 called the Encyclopaedia of Antiquity ; even Aris- 

 totle himself is much in the habit of enumerating 

 the opinions of those who had preceded him. To 

 present such statements as an important part of 

 physical philosophy, shows an erroneous and loose 

 apprehension of its nature. For the only proof 

 of which its doctrines admit, is the possibility of 

 applying the general theory to each particular 

 case : the authority of great men, which in moral 

 and practical matters may or must have its weight, 

 is here of no force; and the technical precision 

 of ideas which the terms of a sound physical theory 

 usually demand, renders a mere statement of the 

 doctrines very imperfectly intelligible to readers 

 familiar with common notions only. To dwell 

 upon such collections of opinions, therefore, both 



