400 FALLACIES. 



one of his absurd physicians say, &quot; 1 opium endorinit 

 parcequ il a une vertu soporifique,&quot; or, in the equivalent 

 doggrel, 



Mihi a docto doctore, 



Domandatur causam et rationem quare 

 Opium facit dormire. 



A quoi respondeo, 



Quia est in eo 



Virtus dormitiva, 

 Cujus est natura 



Sensus assoupire. 



The words Nature and Essence are grand instruments of 

 this mode of begging the question. As in the well-known 

 argument of the scholastic theologians, that the mind thinks 

 always, because the essence of the mind is to think. Locke 

 had to point out, that if by essence is here meant some pro 

 perty which must manifest itself by actual exercise at all 

 times, the premise is a direct assumption of the conclusion ; 

 while if it only means that to think is the distinctive property 

 of a mind, there is no connexion between the premise and the 

 conclusion, since it is not necessary that a distinctive property 

 should be perpetually in action. 



The following is one of the modes in which these abstract 

 terms, Nature and Essence, are used as instruments of this 

 fallacy. Some particular properties of a thing are selected, 

 more or less arbitrarily, to be termed its nature or essence ; 

 and when this hasbeen done, these properties are supposed to 

 be invested with a kind of indefeasibleness ; to have become 

 paramount to all the other properties of the thing, and inca 

 pable of being prevailed over or counteracted by them. As 

 when Aristotle, in a passage already cited, &quot; decides that 

 there is no void on such arguments as this : in a void there 

 could be no difference of up and down; for as in nothing 

 there are no differences, so there are none in a privation or 

 negation; but a void is merely a privation or negation of 

 matter; therefore, in a void, bodies could not move up and 

 down, which it is in their nature to do.&quot;* In other words ; 

 it is in the nature of bodies to move up and down, ergo any 



* Hist. Ind. Sc. i. 34. 



