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AT this stage of our advancement, we may again advert to the idea of power, which we have already examined and defined in the third chapter. The consideration of its origin was then deferred, and to this we now proceed, without repeating any of our former observations. And here I crave some indulgence, on account of the extreme difficulty of applying language at all to so subtle an investigation. There are some mathematical reasonings which are too abstruse to be expressed in words: It is conceivable that, in the most abstruse of all metaphysical inquiries, words may fail to convey the full meaning intended. I hope not so much to be able fully to unfold in language the origin of this idea, as to suggest a hint which may lead the reader's mind to pursue it for himself, if, perhaps, he may get a glimpse of the truth upon this point. I disclaim the expectation of being able to lay down the matter so plainly,

as to be liable to no objection from those who are disposed to cavil. But I refer all cavillers to my third chapter, where they will find the idea defended, though not its origin explained.

It is obvious that the idea of power is not positive, that is, we do not know what power is: -it is something removed from the observation of our senses. The idea is a deduction of the judgment from the changes which we observe. Now we have considered judgment as the power of accurately perceiving the agreement or repugnance of any two conceptions compared together. But it is manifest that judgment can perceive no necessary agreement between any one cause and its effect, as between the application of a spark and the explosion of gunpowder, or the application of heat and the melting of snow. We require experience to inform us what causes will produce what effects. Neither can we perceive any necessary agreement between the idea of a particular power and that of the agent in which it resides, since this would imply a more fundamental knowledge of the nature of the agent than we can ever possess. We need not, therefore, seek for the origin of the idea of power in this way. It is plain also, that, unless the idea were a positive one, we could not derive it from the perception of agreement of any kind. Negative ideas arise from the perception of repugnance among certain conceptions of the mind.

If we should observe a ball moving regularly onwards suddenly to stop, our minds would be arrested by its change of condition, as much as if we observed a ball at rest suddenly to assume a regular motion. The ideas of motion and rest are repugnant to one another: but in the sudden transition they are brought into a successional agreement in the same substance. In the observation of this successional agreement the mind feels a vacuity, a want of satisfaction; because rest and motion are, at the same time, intuitively discerned to be repugnant to one another. The agreement is, therefore, known to be foreign to the several parts of this event; but, as it is not the less real, we are forced to assign it to something unknown, which may serve as a reason of the event, that is, which may satisfy the demand of the mind, and supply the vacuity of which it is conscious, by harmonizing the otherwise discordant parts of the sequence. To this unknown something we give the name of power, and the substance in which we suppose it to exist is denominated a cause; but the name of cause is not applied to it, except when viewed in connection with its effect.


This principle with regard to motion and rest, has been stated in another form by Sir Isaac Newton under the name of the vis inertia of matter, a name which is somewhat objectionable, as the law arises not from any power of matter,

but from the necessary repugnance of motion and rest, and the impossibility of any successional agreement between them in the same piece of matter, without the intervention of foreign power. But the name of vis inertia is short, and, though not quite correct, has suited the purpose very well. Inertia alone would not have contained the whole meaning of Newton, since that would only express the indifference of matter to either of the two states, without so forcibly calling the attention to the impossibility of a change of state taking place, without the intervention of foreign power.

I have adverted to this law because it may be considered as a particular case of a more general proposition. The ideas of state and change are intuitively discerned to be repugnant to one another. The vis inertia expresses that repugnance as exemplified in mechanical philosophy: - But in chemistry, in pneumatology, in every thing, the same mutual repugnance of state and change exists; and, wherever we see these brought into successional agreement in the same substance, knowing that agreement to be foreign to the several parts of the sequence, we attribute it to something unknown called power, with which our mind rests satisfied as the reason of the sequence. Hence it follows that every thing must continue in the state which it is in, whether that state be motion or rest, motion quick or slow, in this direction or in that, solidity or fluidity, life or death,

unless disturbed by some power. Or, in other words, wherever there is a change there must be a


It were vain for me to attempt to render this dark subject clearer by multiplying words. If the reader will revolve these few remarks over and over in his mind, I think he may get a glimpse of the origin of the idea of power, although I am not sure that I have been able adequately to express my meaning. If, however, some should think that the origin of the idea in question is not explained by these considerations, I must just beg of them to enlarge at once the definition of judgment, and to suppose that, in the formation of this idea, it does more than discern agreement or repugnance. The method of rejecting the idea because its origin may not have been accounted for, has been formerly shown to be wholly absurd and unphilosophical.*

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