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standing, than the present? For surely, if there be any relation among obječts, which it imports us to know perfectly, 'tis that of cause and effect. On this are founded all our reasonings concerning matter of fact or existence. By means of it alone we at. tain any assurance concerning objects, which are remov'd from the present teftimony of our memory and senses. The only immediate utility of all sciences is to teach us, how to controul and regulate future events by their causes. Our thoughts and enquiries are, therefore, every moment employ'd about this relation. And yet so imperfect are the ideas which we form concerning it, that 'tis impossible to give any just definition of cause, except what is drawn from some thing extraneous and foreign to it. Similar objects are always conjoin'd with similar. Of this we have experience. Suitable to this experience, therefore, we may define a cause to be an object, follow'd by another, and where all the objects, fimilar to the firsi, are follow'd by obječts, fimilar to the Second: Or in other words, where, if the first object had not been, the second never had: existed: The appear. ance of a cause always conveys the mind, by a customary transition, to the idea of the effect. Of this also we have experience. We may, therefore, fuitable to this experience, form another definition of cause, and call it, an object, follow'd by another, and whose appearance always conveys the thought to that VOL. II.

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other. But tho' both these definitions be drawn from circumstances, foreign to the cause, we cannot remedy this inconvenience, or attain any more perfect definition, which may point out that circumstance in the cause, which gives it a connexion with its effect. We have no idea of this connexion; nor even any diftinct notion what it is we desire to know, when we endeavour at a conception of it. We say, for instance, that the vibration of this string' is the cause of this particular sound. But what do we mean by that affirmation ? We either mean, that this vibration is follow'd by this found, and that all similar vibrations have been follow'd by similar founds : Or, that this vi. bration is foliow'd by this found, and that upon the appearance of cne, the mind anticipates the senses, and forms immediately an idea of the other. We may consider the relation of cause and effect in either of these two lights; but beyond these, we have no idea of it *

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* According to these explications and definitions, the idea of power is relative as much as that of cause; and both have a reference to an effect, or some other event constantly conjoin'd with the former. When we consider the unknown circumstance of an object, by which the degree or quantity of its effect is fixt and determin'd, we call that its power : And accordingly, 'tis allow'd by all philosophers, that the effect is the measure of the power. But if they had any idea of power, as it is in itself, why could not they measure it in itself? The dispute, whether the force of a body in motion be as its velocity or the square of its velocity; this dispute, I say, needed not be decided by comparing its ef

feets

To recapitulate, therefore, the reasonings of this effay : Every idea is copy'd from some preceding impression or sentiment; and where we cannot find any impression, we may be certain that there is no idea. In all single instances of the operation of bodies or minds, there is nothing that produces any impression, nor consequently can suggest any idea, of power or necessary connexion. But when many uniform instances appear, and the same object is always follow'd by the same event; we then begin to entertain the notion of cause and connexion. We then feel a new sentiment or impression, viz. a customary connexion

fects in equal or unequal times; but by a direa mensuration and comparison.

As to the frequent use of the words, Force, Power, Energy, &c. which every where occur in common conversation, as well as in philosophy ; that is no proof, that we are acquainted, in any instance, with the connecting principle betwixt cause and effect, or can account ultimately for the pro. duction of one thing by another. These words, as commonly us'd, have very loose meanings, annex'd to them; and their ideas are very uncertain and confus'd. No animal can put external bodies in motion without the sentiment of a Nilus or endeavour ;, and every animal has a sentiment or feeling from the stroke or blow 'of an external object, that is in motion. These sensations, which are merely animal, and from which we can à priori draw no inference, we are apt to transfer to inanimate objects, and to suppose, that they have some such feelings, whenever they transfer or receive mo. tien, With regard to energies, which are exerted, without our annexing to them any idea of communicated motion, we .consider only the constant experienc'd conjunction of the events; and as we feel a customary connexion betwixt the ideas, we transfer that feeling to the objects ; as nothing is more usual than to apply to external bodies every internal sensation, which tbey occasion.

in the thought or imagination betwixt one object and its usual attendant; and this sentiment is the original of that idea which we seek for. For as this idea arises from a number of similar instances, and not from any single instance; it muft arise from that circumstance, in which the number of instances differ from every individual instance. But this customary connexion or transition of the imagination is the only circumstance, in which they differ. In every other particular they are alike. The first instance which we saw of motion, communicated by the shock of two billiard balls (to return to this obvious instance) is exactly similar to any instance that may, at present, occur to us ; except only, that we could not, at first, infer one event from the other ; which we are enabled to do at present, after so long a course of uniform experience. I know not, if the reader will readily apprehend this reasoning. I am afraid, that, should I multiply words about it, or throw it into a greater variety of lights, it would only become more obscure and intricate. In all abftract reasonings, there is one point of view, which, if we can happily hit, we shall go farther towards illustrating the subject, than by all the eloquence and copious expression in the world. This we should endeavour to attain, and reserve the flowers of rhetoric for subjects, which are more adapted to them.

ESSAY

ESS A Y VIII.

Of Liberty and NECESSITY.

PART I.

TT might reasonably be expected, in questions, I which have been canvass’d and disputed with great eagerness since the first origin of science and philosophy, that the meaning of all the terms, at least, should have been agreed upon among the disputants ; and our enquiries, in the course of two thousand years, been able to pass from words to the true and real subject of the controversy. For how casy may it seem to give exact definitions of the terms employ'd in reasoning, and make these definitions, not the mere found of words, the object of future scrutiny and examination ? But if we consider the matter more narrowly, we shall be apt to draw a quite opposite conclusion. From that circumstance alone, that a controversy has been long kept on foot,

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