INTRODUCTION. 



Nature, that word so often spoken as though it referred to a special 

 entity, cannot be for us more than the totaUty of objects comprising : 

 (1) all existing physical bodies ; (2) the general and special laws, 

 which regulate the changes of state and position to which these bodies 

 are hable ; (3) lastly, the movement distributed at large among them, 

 which is continually preserved or being renewed, has infinitely varied 

 effects, and gives rise to that wonderful order of things which this 

 totahty embodies. 



All physical bodies whatever — sohd, fluid, liquid or gaseous— are 

 endowed with properties and faculties pecuhar to themselves ; but as a 

 result of the movement distributed among them, these bodies are hable 

 to different relations and transformations in their state and position. 

 They are hable to contract with one another various kinds of union, 

 combination or aggregation, and then to undergo all kinds of altera- 

 tions, such as complete or incomplete separation from their other 

 components or from their aggregates, etc. ; these bodies thus derive 

 new properties and faculties from the condition in which each of them 

 is placed. 



As a further result of the arrangement or position of these same 

 bodies, of their special condition at any period of time, of the faculties 

 possessed by each, of the laws of all the orders which regulate their 

 changes and effects, and, lastly, of the movement which never leaves 

 them in absolute rest, there continually reigns throughout the whole 

 of nature a mighty activity, a succession of movements and trans- 

 formations of all kinds, which nothing could arrest or annihilate, 

 unless it be the power which has made all things exist. 



The idea of nature as eternal, and hence as having existed for all 

 time, is for me an abstract opinion without foundation, finahty or 

 probabihty, and with which my reason could never be satisfied. Since 

 I can have no positive knowledge on this subject, and no power of 

 reasoning about it, I prefer to think that the whole of nature is only 

 an effect : hence, I imagine and hke to beheve in a First Cause or, in 



