MATTER AND ITS PHYSICAL PROPERTIES. 



35 



ities must exist on the surfaces which move in contact with each other, which J 

 must resist, gradually diminish, and ultimately destroy, the motion. 



Independently of the obstructions to the continuation of motion arising from J 

 friction, there is another impediment to which all motions on the surface of j 

 the earth are liable — the resistance of the air. How much this may affect the 

 continuation of motion, appears by many familiar effects. On a calm day, carry j 

 an open umbrella with its concave side presented in the direction in which you 

 are moving, and a powerful resistance will be opposed to your progress, which { 

 will increase with every increase of the speed with which you move. 



We are not, however, without direct experience to prove that motions when 

 unresisted will for ever continue. In the heavens we find an apparatus, which 

 furnishes a sublime verification of this principle. There, removed from all j 

 casual obstructions and resistances, the vast bodies of the universe roll on in 

 their appointed paths, with unerring regularity, preserving without diminution 

 all that motion which they received at their creation from the Hand which 

 launched them into space. This alone, unsupported by other reasons, would 

 be sufficient to establish the quality of inertia ; but viewed in connexion with 

 the other circumstances previously mentioned, no doubt can remain that this is 

 a universal law of nature. 



Organized bodies endued with the living principle, seem to be the only ex- 

 ceptions to this law. But even in these their members and all their compo- 

 nent parts, separately considered, are inert, and are subject to the same laws 

 as all other forms of matter. The quality of animation, from which they derive 

 the power of spontaneous action or voluntary motion, does not belong to the 

 parts, but to the whole, and not to the whole by any obvious or necessary con- 

 nexion, because it is absent in sleep, and totally removed by death, even while 

 the organization of every part remains, to all appearance, without derangement. 

 Seeing, then, the whole visible material universe partaking in the common 

 quality of inertia, unable to trace the conditions of life to any material phenom- 

 ena, it is impossible not to conclude that the will of animated beings is the re- 

 sult of an immaterial principle, which, during the period of life, governs their 

 organized bodies. In what this principle consists, what is its seat, or by 

 what modes of action it moves the body, we are wholly unable to decide. But 

 the same principle — analogy — which guides our investigations in every other 

 part of physical science, ought to govern us in this ; and by that principle, the 

 spontaneous motion found in animated beings, but which in no instance is mani- 

 fested by mere matter, must be attributed, not to the matter which composes 

 the bodily forms of these beings, but to something of altogether a different 

 nature. 



Independently of this, which may be considered as the reasoning proper to 

 physical science, philosophers have given another reason for assigning anima- 

 tion to an immaterial principle. The will, from the very nature of its acts, 

 must belong to a simple, uncompounded, and indivisible being, and conse- 

 quently can never be an attribute of a thing which in its essence is the very 

 reverse of this. 



It has been proved that an inability to change the quantity of motion is a 

 consequence of inertia. The inability to change the direction of motion is 

 another consequence of this quality. The same cause which increases or di- 

 minishes motion, would also give motion to a body at rest ; and therefore we 

 inferred that the same inability which prevents a body from moving itself, will 

 also prevent it from increasing or diminishing any motion which it has re- 

 ceived. In the same manner we can show that any cause which changes the 

 direction of motion would also give motion to a body at rest ; and therefore if a 

 body change the direction of its own motion, the same body might move itself 



