OF NATURAL PHILOSOPHY. 81 



the falsehood of the facts alleged in their support, 

 or by showing how the appearances, which seem to 

 countenance them, are more satisfactorily accounted 

 for without their admission. But it is unfortun- 

 ately the nature of prejudices of opinion to ad- 

 here, in a certain degree, to every mind, and to some 

 with pertinacious obstinacy, pigris radicibus, after all 

 ground for their reasonable entertainment is de- 

 stroyed. Against such a disposition the student of 

 natural science must contend with all his power. Not 

 that we are so unreasonable as to demand of him an 

 instant and peremptory dismission of all his former 

 opinions and judgments ; all we require is, that he 

 will hold them without bigotry, retain till he shall 

 see reason to question them, and be ready to resign 

 them when fairly proved untenable, and to doubt 

 them when the weight of probability is shown to lie 

 against them. If he refuse this, he is incapable of 

 science. 



(71.) Our resistance against the destruction of 

 the other class of prejudices, those of sense, is com- 

 monly more violent at first, but less persistent, than 

 in the case of those of opinion. Not to trust the 

 evidence of our senses, seems, indeed, a hard con- 

 dition, and one which, if proposed, none would com- 

 ply with. But it is not the direct evidence of our 

 senses that we are in any case called upon to reject, 

 but only the erroneous judgments we unconsciously 

 form from them, and this only when they can be 

 shown to be so by counter evidence of the same sort; 

 when one sense is brought to testify against another, 

 for instance ; or the same sense against itself, and 

 the obvious conclusions in the two cases disagree, so 



