154 LIMITS AND FLUXIONS 



of our Faculties, and not from any inconsistency in 

 the nature of the thing" ; these quantities "escape 

 our imagination. " Referring to imaginaries, a J — i 

 in the solution of cubie equations, Colson says 

 (PP- 338-9)* "These impossible quantities . . . 

 are so far from infecting or destroying the truth of 

 these Conclusions, that they are the necessary 

 means and helps of discovering it. And why may 

 we not conclude the same of that other species of 

 impossible quantities, if they must needs be thought 

 and call'd so ? . . . Therefore the admitting and 

 retaining these Quantities . . . 'tis enlarging the 

 number of general Principles and Methods, which 

 will always greatly contribute to the Advancement 

 of true Science. In short, it will enable us to make 

 a much greater progress and proflcience, than we 

 otherwise can do, in cultivating and improving what 

 I have elsewhere call'd The Philosophy of Quantity, " 

 151. A review 1 of this book contains the follow- 

 ing historical exposition. Sir Isaac Newton, 1665, 

 " found the Proportions of the Increments of inde- 

 terminate Quantities. These Increments or Aug- 

 menta Momentanea he called Moments, which others 

 called Particles, infinitely small Parts, and Indi- 

 visibles ; and the Velocities by which the Quantities 

 increased he called Motions, Velocities of Increase, 

 and Fluxions. He considered Quantities not as 

 composed of Indivisibles, but as generated by locai 

 Motion, after the manner of the Ancients . . . and 

 represented such Moments [of Time] by the Letter 0, 



^ Republick of Letters, Art. XI, pp. 223-235, 1736. 



