66 THE REIGN OF LAW. 



the word Law should be clearly distinguished that 

 each of them must be more fully considered by 

 itself. 



The First and, so to speak, the lowest sense in 

 which Law is applied to natural phenomena is 

 that in which it is used to express simply " an 

 observed Order of facts" — that is to say, facts 

 which under the same conditions always follow 

 each other in the same order. In this sense the 

 laws of Nature are simply those facts of Nature 

 which recur according to a rule. It is not ne- 

 cessary to the legitimate application of Law 

 in this sense, that the cause of any observed 

 Order of facts should be at all known, or even 

 guessed at. The force or forces to which that 

 Order is due may be hid in total darkness. It 

 is sufficient that the Order or sequence of phe- 

 nomena be uniform and constant. The neatest 

 and simplest illustration of this, as well as of 

 the other senses in which Law is used, is to be 

 found in the exact sciences, and especially in 

 the history of Astronomy. It is nearly 250 years 

 since Kepler discovered, in respect to the dis- 

 tances, velocities, and orbits of the Planets, three 



