96 DISCOURSE ON THE STUDY 



The only difference between these and axioms ob- 

 tained from extensive induction is this, that, in 

 raising the axioms of geometry, the instances offer 

 themselves spontaneously, and without the trouble 

 of search, and are few and simple ; in raising 

 those of nature, they are infinitely numerous, com- 

 plicated, and remote ; so that the most diligent 

 research and the utmost acuteness are required 

 to unravel their web, and place their meaning in 

 evidence. 



(87.) By far the most general phenomenon with 

 which we are acquainted, and that which occurs 

 most constantly, in every enquiry into which we 

 enter, is motion, and its communication. Dynamics, 

 then, or the science of force and motion, is thus 

 placed at the head of all the sciences ; and, hap- 

 pily for human knowledge, it is one in which 

 the highest certainty is attainable, a certainty no 

 way inferior to mathematical demonstration. As 

 its axioms are few, simple, and in the highest de- 

 gree distinct and definite, so they have at the same 

 time an immediate relation to geometrical quantity, 

 space, time, and direction, and thus accommodate 

 themselves with remarkable facility to geometrical 

 reasoning. Accordingly, their consequences may be 

 pursued, by arguments purely mathematical, to any 

 extent, insomuch that the limit of our knowledge 

 of dynamics is determined only by that of pure 

 mathematics, which is the case in no other branch of 

 physical science. 



(88.) Bu.t, it will now be asked, how we are tb 

 proceed to analyse a composite. phenomenon into 

 simpler ones, and whether any general rules can be 



