SO ESSAY ON PROBABILITIES. 



that there is no such thing. The term probability is 

 as difficult to explain as gravitation : and the method of 

 proceeding is the same with regard to the properties of 

 both. We cannot tell what they are, in simpler terms, 

 but we know them by, or rather trace and define them 

 by, their manifestations. In both, we first see a com- 

 pound result, depending upon the patient as well as the 

 agent. In the case of the mental phenomena, we can- 

 not decompose the effect produced, still less ascend a 

 step, and find any of the laws which regulate the hu- 

 man disposition to doubt or expect. I shall conclude by 

 again reminding the reader, that the impression produced 

 by circumstances upon his own mind is the thing in 

 uestion ; and that nothing can be more liable to cause 

 confusion than a lurking notion that the results of theory 

 are anything more, before the event arrives, than a re- 

 presentation of the relative force of his own impressions, 

 as they should be if unassisted reason could follow the le- 

 gitimate consequences of some simple and universally 

 admitted principles. 



I proceed in the next chapter to develope the leading 

 rules of the science. 



CHAP. II. 



ON DIRECT PROBABILITIES. 



WE now proceed on the supposition that the probability 

 of an event is measured by the fraction which the 

 number of favourable cases is of all that can happen. 

 Thus, if there be 20 white balls and 27 black (20 + 27 

 or 47 in all), the probability of drawing a white ball is 

 measured by -J-Q-, and that of drawing a black ball by ~^L. 

 We shall say that these probabilities are |^ and |^. 

 Nothing is more common than to substitute a measure 



