in Natural History. 217 



culiar attributes independently of individuals. This faculty 

 of the mind, which is one of the most curious that belongs to 

 it, has given rise in all languages to a multitude of words of 

 the same kind as the names of genera in Natural History ; 

 words, which do not express individual existences, but are 

 abstractions of qualities and characters belonging to them *. 



All general reasoning in morality, law, politics, and even 

 mathematics, depends for its accuracy upon the proper use of 

 generic and other abstract terms. In mathematics they admit 

 of exact (or I would rather say more exact) previous defini- 

 tion; and hence arises the accuracy of deductions the most 

 recondite and remote in that science. In the other sciences, 

 which are of a speculative and contingent nature, these terms 

 are employed not with the same precision, but seem to be the 

 result of our necessities, borrowed from sensible objects and 

 analogy, and frequently indeed from accidental coincidences. 

 They derive their force rather from the character of the mind 

 that employs them, than from any exact definition they may 

 have received ; and it seems impossible to make men use such 

 words in a common acceptation. Hence it is, I apprehend, that 

 knowledge of a speculative kind so soon finds its limits; and 

 where at its outset it has promised such glorious results to 

 mankind, as long as it floated in general propositions, the same 

 subject eludes the grasp of the human faculties when it is at- 

 tempted to be reduced to exactness, and leaves something al- 

 ways to be desired. We are constantly approximating to the 

 truth, yet never reaching it. 



It is sometimes asserted, but not correctly, that Natural 

 History, by the aid of its terms, partakes of the nature of ma- 

 thematical truth; or that it lies intermediate between that 

 science and speculative knowledge. The situation of the na- 

 turalist is rather this. He finds himself placed amidst an in- 

 finite number of unknown particulars ; and in order to facili- 

 tate an acquaintance with them, he at once, without regarding 

 individuals with much minuteness, throws together a number 

 of them, which he calls a species, according to an assumed 

 hypothesis. These he attempts again to combine by certain 

 external characters, and calls them a genus. By these means 

 he is enabled to contemplate and treat of them, without being 

 utterly bewildered in the labyrinth of unarranged individuals. 

 Classification is his^filum Ariudneum. It was but imperfectly 

 understood by the ancients ; and has enabled the moderns to 

 arrive at conclusions with much more expedition than they, 



* I would avoid here, and leave the question to be decided by the 

 reader, after he has consulted Locke and Berkeley, whether we have got 

 ideas corresponding to these abstract terms, or whether they are mere 

 signs, like #, y y and z, in algebra. 



New Series. Vol. 3. No. 14. March 1828. 2 F and 



