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always many other effects, which, to reason,' must seem fully as confistent and natural. In vain, therefore, should we pretend to determine any single event, or infer any cause or effect, without the assistance of observation and experience.

Hence we may discover the reason, why no philosopher, who is rational and modest, has ever pretended to assign the ultimate cause of any natural operation, or to show distinąly the action of that power, which produces any single effect in the universe. 'Tis confessed, that the utmost effort of human reason is, to reduce the principles, productive of natural phænomena, to a greater fimplicity, and to resolve the many particular effects into a few general causes, by means of reasonings from analogy, experience, and observation. But as to the causes of these general causes, we should in vain attempt their discovery; nor shall we ever be able to satisfy ourselves, by any particular explication of them., These ultimate springs and principles are totally shut up from human curiosity and enquiry. Elasticity, gravity, cohesion of parts, communication of motion by impulse ; these are probably the ultimate causes and principles which we shall ever discover in nature ; and we may esteem ourselves sufficiently happy, if, by accurate, enquiry and reasoning, we can trace up the particular phænomena to, or near to, these general principles. The most perfect philosophy of the natural kind only removes our ignorance a little further: As perhaps the most perfect philosophy of the moral or metaphysical kind serves only to discover larger portions of our ignorance. Thus the observation of human blindness and weakness is the result of all philosophy, and meets us, at every turn, in spight of our endeavours to elude or avoid it.

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Nor is geometry, when taken into the assistance of natural philosophy, ever able to remedy this defect, or lead us into the knowlege of ultimate causes, by all that accuracy of reasoning, for which it is so justly celebrated. Every part of mixed mathematics goes upon the supposition, that certain laws are established by nature in her operations; and abstract reasonings are employed, either to assist experience in the difcovery of these laws, or to determine their influence in particular instances, where it depends upon any precise degrees of distance and quantity. Thus 'tis a law of motion, discovered by experience, that the moment or force of any body in motion is in the compound ratio or proportion of its solid contents and its velocity; and consequently, that a small force may remove the greatest obstacle or raise the greatest weight, if by any contrivance or machinery we can increase the velocity of that force, so as to make it an overmatch for its antagonist. Geometry assists us in the application of this law, by giving us the just dimensions of all the parts and figures, which can enter into any species of machine; but still the discovery of the law itself is owing merely to experience, and all the abstract reasonings in the world could never lead us one step towards the knowlege of it. When we reason a priori, and consider merely any object or cause, as it appears to the mind, independent of all observation, it never could suggest to us the notion of any distinct object, such as its effect; much less, shew us the inseparable and inviolable connection between them. A man must be very fagacious, who could discover by reasoning, that crystal is the effect of heat, and ice of cold, without being previously acquainted with the operations of these qualitics.

Vol. II.

PART

PART II. . But we have not, as yet, attained any tolerable satisfaction with regard to the question first proposed. Each folution still gives rise to a new question as difficult as the foregoing, and leads us on to farther enquiries. When it is afked, What is the nature of all our reasonings concerning matter of faiz ? The proper answer seems to be, that they are founded on the relation of cause and effect. When again it is asked, What is the foundation of all our reasonings and conclusions concerning that relation? it may be replied in one word, ExPERIENCE. But if we still carry on our sifting humour, and ask, What is the foundation of all conclusions from experience ? this implies a new question, which may be of more difficult folution and explication. Philosophers, that give themselves airs of superior wisdom and fufficiency, have a hard task, when they encounter persons of inquisitive dispositions, who push them from every corner, to which they retreat, and who are sure at last to bring them to some dangerous dilemma. The best expedient to prevent this confusion, is to be modest in our pretenfions; and even to discover the difficulty ourselves before it is objected to us. By this means, we may make a kind of merit of our very ignorance.

I shall content my self, in this fe&tion, with an easy task, and shall pretend only to give a negative answer to the question here proposed. I say then, that even after we have experience of the operations of cause and effect, our conclusions from that experience are not founded on reasoning, or any process of the understanding. This answer we must endeavour, both to explain and to defend.

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It must certainly be allowed, that nature has kept us at a great distance from all her secrets, and has afforded us only the knowlege of a few superficial qualities of objects, while she conceals from us those powers and principles, on which the influence of these objects entirely depends. Our senses inform us of the colour, weight, and consistence of bread; but neither sense nor reason ever can inform us of those qualities, which fit it for the nourishment and support of a human body. Sight or feeling conveys an idea of the actual motion of bodies; but as to that wonderful force or power, which would carry on a moving body for ever in a continued change of place, and which bodies never lose but by communicating it to others; of this we cannot form the most distant conception. But notwithstanding this ignorance of natural powers * and principles, we always presume, where we see like sensible qualities, that they have like secret powers, and lay our account, that effects, fimilar to those, which we have experienced, will follow from them. If a body of like colour and consistence with that of bread, which we have formerly eat, be presented to us, we make no scruple of repeating the experiment, and expect, with certainty, like nourishment and support. Now this is a process of the mind or thought, of which I would willingly know the foundation. 'Tis allowed on all hands, that there is no known connection between the sensible qualities and the secret powers; and consequently, that the mind is not led to form such a conclusion concerning their constant and regular conjunction, by any thing which it knows of their nature. As to past Experience, it can be allowed to give direct and certain

• The word, Power, is here used in a loose and popular sense. The more accurate explication of it would give additional evidence to this argument. See Seft. 7.

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information only of those precise objects, and that precise period of time, which fell under its cognizance : But why this experience should be extended to future times, and to other objects, which, for aught we know, may be only in appearance similar; this is the main question on which I would infift. The bread, which I formerly eat, nourished me; that is, a body of such sensible qualities, was, at that time, endued with such secret powers: but does it follow, that other bread must also nourish me at another time, and that like sensible qualities must always be attended with like secret powers? The confequence seems nowise necessary. At least, it must be acknowleged, that there is here a consequence drawn by the mind; thạt there is a certain step taken; a process of thought, and am inference, which wants to be explained. These two propositiors are far from being the same, I have found that such an object has always been attended with such an effect, and I foresee, that other objects, which are, in appearance, similar, will be attended with similar effects. I shall allow, if you please, that the one proposition may justly be inferred from the other: I know in fact, that it always is inferred. But if you insist, that the inference is made by a chain of reasoning, I desire you to produce that reasoning. The connection between these propositions is not intuitive. There is required a medium, which may enable the mind to draw such an inference, if indeed it be drawn by reasoning and argument. What that medium is, I must confess, passes my comprehension; and 'tis incumbent on those to produce it, who assert, that it really exists, and is the origin of all our conclusions concerning matter of fact.

This negative argument must certainly, in process of time, become altogether convincing, if many penetrating and able

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