OF NATURAL PHILOSOPHY. 9d 



which most decidedly resist further decomposition, 

 it is evident that the greatest pains and attention 

 ought to be bestowed, not only because they furnish 

 a key to the greatest number of enquiries, and 

 serve to group and classify together the greatest 

 range of phenomena, but by reason of their higher 

 nature, and because it is in these that we must 

 look for the direct action of causes, and the most 

 extensive and general enunciation of the laws or 

 nature. These, once discovered, place in our power 

 the explanation of all particular facts, and become 

 grounds of reasoning, independent of particular 

 trial : thus playing the same part in natural philo- 

 sophy that axioms do in geometry ; containing, in a 

 refined and condensed state, and as it were in a 

 quintessence, all that our reason has occasion to 

 draw from experience to enable it to follow out 

 the truths of physics by the mere application of 

 logical argument. Indeed, the axioms of geometry 

 themselves may be regarded as in some sort an 

 appeal to experience, not corporeal, but mental. 

 When we say, the whole ,is greater than its part, 

 we announce a general fact, which rests, it is 

 true, on our ideas of whole and part ; but, in abs- 

 tracting these notions, we begin by considering 

 them as subsisting in space, and time, and body, 

 and again, in linear, and superficial, and solid space. 

 Again, when we say, the equals of equals are equal, 

 we mentally make comparisons, in equal spaces, 

 equal times, &c.; so that these axioms, however 

 self-evident, are still general propositions so far of 

 the inductive kind, that, independently of experience, 

 they would not present themselves to the mind. 



