270 LIGHT SCIENCE FOR LEISURE HOURS. 



wise with heterodoxy, which relates to instances where 

 general opinion is divided, and a majority only 

 (whether of number or power) favours the orthodox 

 view. In science, however, paradoxy is more often 

 met with than heterodoxy; and as general opinions 

 are not now formed in science without strong evidence, 

 paradoxy is, as a rule, error, only distinguished from 

 other error by being blatant. 



It may be asked, however and is a very suitable 

 inquiry at the outset how we are to assure ourselves 

 that the paradoxist may not be a great discoverer. If 

 the present theory of the universe was called three 

 centuries ago the e paradox of Copernicus,' how can we 

 be sure that the paradox of Reddie, or * Parallax,' or 

 Morrison, may not be the future theory of the uni- 

 verse? The rule is very simple, and is clearly 

 enunciated by De Morgan. * New knowledge,' he says, 

 ' when to any purpose, must come by contemplation of 

 old knowledge, in every matter which concerns thought 

 (mechanical contrivance sometimes, not very often, 

 escapes this rule). All the men who are now called 

 discoverers, in every matter ruled by thought, have 

 been men versed in the minds of their predecessors, 

 and learned in what had been done before them.' 

 (The italics are mine.) 'There is not one excep- 

 tion. ... If any one will undertake to show a person 

 of little or no knowledge who has established himself 

 in a great matter of pure thought, let him bring for- 

 ward his man and we shall see. This is the true way 

 of putting off those who plague others with their great 



