86 SCIENCE AND METHOD. 



how long will it be before this mixture satisfies us ? 

 When shall we have accumulated enough complica- 

 tions ? When will the cards be sufficiently shuffled ? 

 If we mix two powders, one blue and the other white, 

 there comes a time when the colour of the mixture 

 appears uniform. This is on account of the infirmity 

 of our senses ; it would be uniform for the long- 

 sighted, obliged to look at it from a distance, when 

 it would not yet be so for the short-sighted. Even 

 when it had become uniform for all sights, we could 

 still set back the limit by employing instruments. 

 There is no possibility that any man will ever dis- 

 tinguish the infinite variety that is hidden under the 

 uniform appearance of a gas, if the kinetic theory is 

 true. Nevertheless, if we adopt Gouy's ideas on the 

 Brownian movement, does not the microscope seem to 

 be on the point of showing us something analogous ? 



This new criterion is thus relative like the first, and 

 if it preserves an objective character, it is because all 

 men have about the same senses, the power of their 

 instruments is limited, and, moreover, they only make 

 use of them occasionally. 



IX. 



It is the same in the moral sciences, and particularly 

 in history. The historian is obliged to make a selec- 

 tion of the events in the period he is studying, and he 

 only recounts those that seem to him the most im- 

 portant. Thus he contents himself with relating the 

 most considerable events of the i6th century, for 

 instance, and similarly the most remarkable facts of 

 the 17th century. If the former are sufficient to 

 explain the latter, we say that these latter conform 



