AND THEORY OF THE HEAVENS. 35 



accompany me in this adventurous expedition through 

 the physical world on the ground of such probable con- 

 jectures, he will not find in the course of the expedition 

 so many crooked by-paths or insuperable obstacles as he 

 perhaps apprehends at the outset. 



In fact, I have with the greatest carefulness kept clear 

 of all arbitrary hypotheses. After having resolved the 

 world into the simplest chaos, I have applied no other 

 forces than those of attraction and repulsion to the 

 evolution of the great order of nature : two forces which 

 are both equally certain, equally simple, and, at the 

 same time, equally original and universal. They are 

 both borrowed from the Natural Philosophy of Newton. 

 The first is a law of nature, which is now established 

 beyond doubt. The second, which is perhaps not 

 demonstrated by the science of Newton with so much 

 distinctness as the first, is accepted here only in that 

 understanding of it which no one questions, namely, in 

 connection with the finest dissolution of matter, as, for 

 instance, in vapours. It is from these very simple 

 principles that I have deduced the following system in 

 an unfactitious manner, without working out any other 

 consequences than those which must themselves command 

 the attention of the reader. 



Finally, I may be permitted to make a brief explana- 

 tion regarding the validity and the presumed value of 

 the propositions which will appear in the following theory, 

 and by which I wish it to be tested by just judges. It 

 is fair to judge an author by the stamp which he impresses 

 on his wares ; and, therefore, I hope that in the different 

 parts of this treatise no more rigid vindication of my 

 opinions will be demanded than what is in accordance 



