18 ESSAY ON PROBABILITIES. 



two, a or by than that we shall draw a, the argument 

 must be directed against the method of measurement, 

 not against the possibility of a measure : for wherever 

 more or less are applicable terms, twice, thrice, &c. 

 must be also conceived to be possible, whether we can 

 ascertain how to find them or not. But no other 

 method of measurement has ever been proposed, nor, in 

 truth, have the assertors been aware that they could be 

 brought to such close quarters, but have generally ob- 

 jected to the theory as a whole, without any particular 

 knowledge of its parts. It will be time enough to 

 refute their notion, when they begin to be so particular 

 that refutation becomes possible. 



II. That it is not practical. By this it is either 

 meant, (for practical is one of the words employed in 

 shifting an argument, which are sometimes so con- 

 venient), that it has not been reduced to practical 

 form, or else that it is not capable of being so reduced ; 

 or perhaps that it is not useful. The working results 

 hitherto obtained may be divided into : 1 . The method 

 of obtaining probabilities. 2. The method of estimating 

 the probability of more or less departure from the 

 results indicated by the main branch of the theory as 

 most probable. The first has been frequently made 

 practical ; the second not hitherto, except to mathema- 

 ticians. That the whole can be made practical, I hope 

 to establish by the contents of this work. To the asser- 

 tion that it is not useful, we oppose : 1 . The unanimous 

 opinion of astronomers, (meaning thereby persons capa- 

 ble of applying the subject to astronomy) that the 

 exactness of our present knowledge is very much owing 

 to the application of it, and their uniformly continuing 

 to use it in the deduction of results from the necessary 

 discordances of observations. 2. The extent to which 

 it has been applied in the very choicest view of 

 the word practical, (which frequently means money- 

 making) in concerns which now employ many millions 

 sterling. 3. The light in which it is regarded by a 

 very large majority of those who have studied it, as a 



