SECTION VII.

Of the IDEA of NECESSARY CONNEXION.

PART I.

HE great advantage of the mathematical sci

THE

ences above the moral confists in this, that the ideas of the former, being fenfible, are always clear and determinate, the smallest diftinction between them is immediately perceptible, and the fame terms are ftill expreffive of the fame ideas, without ambiguity or variation. An oval is never mistaken for a circle, nor an hyperbola for an ellipfis. The ifofceles and scalenum are distinguished by boundaries more exact than vice and virtue, right and wrong. If any term be defined in geometry, the mind readily, of itfelf substitutes, on all occafions, the definition for the term defined: Or even when no definition is employed, the object itself may be prefented to the fenfes, and by that means be fteadily and clearly apprehended. But the finer fentiments of the mind, the operations of the understanding, the various agitations of VOL. III.

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the paffions, tho' really in themselves diftinct, eafily efcape us, when furveyed by reflection; nor is it in our power to recall the original object, as often as we have occafion to contemplate it. Ambiguity, by this means, is gradually introduced into our reasonings: Similar objects are readily taken to be the fame: And the conclufion becomes at last very wide of the premifes.

ONE may fafely, however, affirm, that, if we confider thefe sciences in a proper light, their advantages and disadvantages very nearly compenfate each other, and reduce both of them to a state of equality. If the mind with greater facility retains the ideas of geometry clear and determinate, it must carry on a much longer and more intricate chain of reasoning, and compare ideas much wider of each other, in order to reach the abftrufer truths of that fcience. And if moral ideas are apt, without extreme care, to fall into obfcurity and confufion, the inferences are always much fhorter in these difquifitions, and the intermediate steps, which lead to the conclufion, much fewer than in the sciences which treat of quantity and number. In reality, there is scarce a propofition in EuCLID fo fimple, as not to confist of more parts, than are to be found in any moral reasoning which runs not into chimera and conceit. Where we trace the principles of the human mind thro' a few fteps, we may be very well fatisfied with our progrefs; confi

dering how foon nature throws a bar to all our in. quiries concerning caufes, and reduces us to an acknowledgment of our ignorance. The chief obsta cle, therefore, to our improvement in the moral or metaphyfical sciences is the obfcurity of the ideas, and ambiguity of the terms. The principal difficulty in the mathematics is the length of inferences and compafs of thought, requifite to the forming any conclufion. And perhaps, our progress in natural philofophy is chiefly retarded by the want of proper expe riments and phænomena, which often are discovered by chance, and cannot always be found, when requifite, even by the moft diligent and prudent inquiry. As moral philofophy feems hitherto to have received lefs improvements than either geometry or phyfics, we may conclude, that, if there be any difference in this refpect among thefe fciences, the difficulties, which obftruct the progrefs of the former, require fuperior care and capacity to be furmounted.

THERE are no ideas, which occur in metaphyfics, more obfcure and uncertain, than thofe of power, force, energy, or neceffary connexion, of which it is every moment neceffary for us to treat in all our difquifitions. We fhall, therefore, endeavour, in this fection, to fix, if poffible, the precife meaning of these terms, and thereby remove fome part of that obfcurity, which is fo much complained of in this fpecies of philofophy.

Ir feems a propofition, which will not admit of much difpute, that all our ideas are nothing but copies of our impreffions, or, in other words, that 'tis impoffible for us to think of any thing, which we have not antecedently felt, either by our external or internal fenfes. I have endeavoured* to explain and prove this propofition, and have expressed my hopes, that, by a proper application of it, men may reach a greater clearness and precifion in philofophical reafonings, than what they have hitherto been ever able to attain. Complex ideas may, perhaps, be well known by definition, which is nothing but an enumeration of thofe parts or fimple ideas, that compofe them. But when we have pushed up definitions to the moft fimple ideas, and find ftill fome ambiguity and obfcurity; what refource are we then poffeffed of? By what invention can we throw light upon thefe ideas, and render them altogether precife and determinate to our intellectual view? Produce the impreffions or original fentiments, from which the ideas are copied. Thefe impreffions are all ftrong and fenfible. They admit not of ambiguity. They are not only placed in a full light themselves, but may throw light on their correfpondent ideas, which lie in obfcurity. And by this means, we may, perhaps, attain a new microscope or fpecies of optics, by which, in the moral sciences, the most minute, and most fimple ideas may be fo en

* Section II.

larged

larged as to fall readily under our apprehenfion, and be equally known with the groffeft and moft fenfible ideas, which can be the object of our inquiry.

To be fully acquainted, therefore, with the idea of power or neceffary connexion, let us examine its im preffion; and in order to find the impreffion with greater certainty, let us fearch for it in all the fources, from which it may poffibly be derived.

WHEN We look about us towards external objects, and confider the operation of caufes, we are never able, in a single instance, to discover any power or neceffary connexion; any quality, which binds the effect to the cause, and renders the one an infallible confequence of the other. We only find, that the one

does actually, in fact, follow the other.

The impulse of one billiard-ball is attended with motion in the fe cond. This is the whole that appears to the outward fenses. The mind feels no fentiment or inward impreffion from this fucceffion of objects: Confequently, there is not, in any fingle, particular inftance of caufe and effect, any thing which can suggest the idea of power or necessary connexion.

FROM the first appearance of an object, we never can conjecture what effect will refult from it. But were the power or energy of any cause discoverable by the mind, we could foresee the effect, even without experience,

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