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Of the IDE A Of necessary Connexion.


T HE great advantage of the mathematical scie

ences above the moral consists in this, that the ideas of the former, being fensible, are always clear and determinate, the smallest distinction betwixt them is immediately perceptible, and the same terms are still expreflive of the same ideas, without ambiguity or variation. An oval is never mistaken for a circle, nor an hyperbola for an ellipsis. The isosceles and scalenum are diftinguish'd by boundaries more exact than vice and virtue, right and wrong. If any term be defin'd in geometry, the mind readily, of itself, substitutes, on all occasions, the definition for the term defin'd: Or even when no definition is VOL. II.


employ'd, the object itself may be presented to the senses, and by that means be steadily and clearly apprehended. But the finer sentiments of the mind, the operations of the understanding, the various agitations of the passions, tho'really in themselves diftinet, easily escape us, when survey'd by reflection ; nor is it in our power to recall the original object, as often as we have occasion to contemplate it. Ambiguity, by this means, is gradually introduc'd into our reasonings: Similar objects are readily taken to be the same : And the conclusion becomes, at last, very wide of the premises.

One may safely, however, affirm, that if we con. sider these sciences in a proper light, their advan. tages and disadvantages very nearly compensare each-cther, 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 science. And if moral ideas are apt, without extreme care, to fall into obscurity and confusion, the inferences are always much shorter in these disquisitions, and the intermediate steps, which lead to the conclu. fion, much fewer than in the sciences, which treat of quantity and number. In reality, there is fcarce proposition of Euclid fo simple as not to consift 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 heps, we may be very well satisfy'd with our progress; if we consider how fuon nature throws a bar to all our enquiries concerning causes, and reduces us to an acknowlegement of our ignorance. The chief obstacle, therefore, to our improvement in the moral or meta- · physical sciences is the obscurity of the ideas, and ambiguity of the terms. The principal difficulty in the mathematics is the length of inferences and compass of thought, requisite to the forming any conclufion. And perhaps, our progress in natural philosophy is chiefly retarded by the want of proper experiments and phænomena,which often.are discover'd by chance, and cannot always be found, when requisite, even by the mok diligent and prudent enquiry. As moral philosophy seems hitherto to have received less improvements than either geometry or physics, we may conclude, that, if there be any difference in this re. fpect among these sciences, the difficulties, which obAruct the progress of the former, require superior care and capacity to be surmounted.

a pro

There are no ideas, which occur in metaphysics, more obscure and uncertain, than those of power, force, energy, or necessary.conxexion, of which it is every

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moment neceffary for us to treat in all our disquifitions. We shall, therefore, endeavour, in this essay, to fix, if posible, the precise meaning of these terms, and thereby remove some part of that obscurity, which is so much complain’d of in this species of philosophy.

It seems a proposition, which will not admit of much dispute, that all our ideas are nothing but co. pies of our impressions, or in other words, that 'tis impossible for us to think of any thing, which we have not antecedently felt, either by our external or internal senses. I have endeavour'd in a former es. say * to explain and prove this proposition, and have express’d my hopes, that, by a proper application of it, men may reach a greater clearness and precision in philosophical reasonings, 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 those parts or simple ideas, that compose them. But when we have push'd up definitions to the most simple ideas, and find still fome ambiguity and obscurity; what resource are we then poffess'd of? By what invention can we throw light upon these ideas, and render them altogether precise and determinate to our intel


* Efray II.

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