314 REASONING. 



sible, which is in contradiction to long established 

 and familiar experience ; or even to old and familiar 

 habits of thought. And this difficulty is a necessary 

 result of the fundamental laws of the human mind. 

 When we have often seen and thought of two things 

 together, and have never in any one instance either 

 seen or thought of them separately, there is by the 

 primary law of association an increasing difficulty, 

 which in the end becomes insuperable, of conceiving 

 the two things apart. This is most of all conspicuous 

 in uneducated persons, who are in general utterly 

 unable to separate any two ideas which have once 

 become firmly associated in their minds ; and if per- 

 sons of cultivated intellect have any advantage on the 

 point, it is only because, having seen and heard and 

 read more, and being more accustomed to exercise 

 their imagination, they have experienced their sensa- 

 tions and thoughts in more varied combinations, and 

 have been prevented from forming many of these 

 inseparable associations. But this advantage has 

 necessarily its limits. The man of the most prac- 

 tised intellect is not exempt from the universal laws 

 of our conceptive faculty. If daily habit presents to 

 him for a long period two facts in combination, and 

 if he is not led during that period either by accident 

 or intention to think of them apart, he will in time 

 become incapable of doing so even by the strongest 

 effort ; and the supposition that the two facts can be 

 separated in nature, will at last present itself to his 

 mind with all the characters of an inconceivable 

 phenomenon. There are remarkable instances of this 

 in the history of science : instances, in which the 

 wisest men rejected as impossible, because incon- 

 ceivable, things which their posterity, by earlier 

 practice and longer perseverance in the attempt, 



