324 FALLACIES. 



Sufficient Eeason. By what right is it assumed that a state 

 of rest is the particular state which cannot be deviated from 

 without special cause ? Why not a state of motion, and of 

 some particular sort of motion ? Why may we not say that 

 the natural state of a horse left to himself is to amble, because 

 otherwise he must either trot, gallop, or stand still, and 

 because we know no reason why he should do one of these 

 rather than another ? If this is to be called an unfair use of 

 the &quot; sufficient reason,&quot; and the other a fair one, there must 

 be a tacit assumption that a state of rest is more natural to a 

 horse than a state of ambling. If this means that it is the 

 state which the animal will assume when left to himself, that 

 is the very point to be proved ; and if it does not mean this, 

 it can only mean that a state of rest is the simplest state, and 

 therefore the most likely to prevail in nature, which is one of 

 the fallacies or natural prejudices we have already examined. 



So again of the First Law of Motion ; that a body once 

 moving will, if left to itself, continue to move uniformly in a 

 straight line. An attempt is made to prove this law by saying, 

 that if not, the body must deviate either to the right or to the 

 left, and that there is no reason why it should do one more than 

 the other. But who could know, antecedently to experience, 

 whether there was a reason or not ? Might it not be the 

 nature of bodies, or of some particular bodies, to deviate 

 towards the right ? or if the supposition is preferred, towards 

 the east, or south ? It was long thought that bodies, terres 

 trial ones at least, had a natural tendency to deflect down 

 wards; and there is no shadow of anything objectionable in 

 the supposition, except that it is not true. The pretended 

 proof of the law of motion is even more manifestly untenable 

 than that of the law of inertia, for it is flagrantly inconsis 

 tent ; it assumes that the continuance of motion in the 

 direction first taken is more natural than deviation either to 

 the right or to the left, but denies that one of these can 

 possibly be more natural than the other. All these fancies 

 of the possibility of knowing what is natural or not natural 

 by any other means than experience, are, in truth, entirely 

 futile. The real and only proof of the laws of motion, or of 



