80 DISCOURSE ON THE STUDY 



notion of what might or what ought to be the order 

 of nature in any proposed case, and content our- 

 selves with observing, as a plain matter of fact, what 

 is. To experience we refer, as the only ground of all 

 physical enquiry. But before experience itself can 

 be used with advantage, there is one preliminary 

 step to make, which depends wholly on ourselves : 

 it is the absolute dismissal and clearing the mind 

 of all prejudice, from whatever source arising, and 

 the determination to stand and fall by the result of 

 a direct appeal to facts in the first instance, and of 

 strict logical deduction from them afterwards. Now, 

 it is necessary to distinguish between two kinds of 

 prejudices, which exercise very different dominion 

 over the mind, and, moreover, differ extremely in 

 the difficulty of dispossessing them, and the process 

 to be gone through for that purpose. These are, 



1. Prejudices of opinion. 



2. Prejudices of sense. 



(69.) By prejudices of opinion, we mean opinions 

 hastily taken up, either from the assertion of others, 

 from our own superficial views, or from vulgar ob- 

 servation, and which, from being constantly ad- 

 mitted without dispute, have obtained the strong 

 hold of habit on our minds. Such were the opinions 

 once maintained that the earth is the greatest body 

 in the universe, and placed immovable in its cen- 

 tre, and all the rest of the universe created for its 

 sole use ; that it is the nature of fire and of sounds 

 to ascend ; that the moonlight is cold ; that dews fall 

 from the air, &c- 



(70.) To combat and destroy such prejudices we 

 may proceed in two ways, either by demonstrating 



