366 FALLACIES. 



think it necessary to prove the law of inertia, they 

 of course do not suppose it to be self-evident; they 

 must, therefore, be of opinion that, previously to all 

 proof, the supposition of a body's moving by internal 

 impulse is an admissible hypothesis: but if so, why 

 is not the hypothesis also admissible, that the internal 

 impulse acts naturally in some one particular direct 

 tion, not in another? ^If spontaneous motion might 

 have been the law oj/matter, why not spontaneous 

 motion towards the sun, towards the earth, or towards 

 the zenith? Why not, as the ancients supposed, 

 towards a particular place in the universe, appro- 

 priated to each particular kind of substance? Surely 

 it is not allowable to say that spontaneity of motion 

 is credible in itself, but not credible if supposed to 

 take place in any determinate direction. 



Indeed, if any one chose to assert that all bodies 

 when uncontrolled set out in a direct line towards the 

 north pole, he might equally prove his point by the 

 principle of the Sufficient Reason. 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 natu- 

 ral 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 " sufficient reason," 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 



