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: THESE loose hints I have thrown together, in order to excite the curiosity of philosophers, and beget a fufpicion at least, if not a fall persuasion, that this sub. ject is very copious, and that many operations of the human mind depend on the connexion or association of ideas, which is here explained. Particularly, the fympathy between the passions and imagination will, perhaps, appear remark. able; while we obferve that the affections, excited by one object, pass easily to another connected with it; but transfuse themselves with difficulty, or not at all, along different objects, which have no manner of connexion together. By introducing, into any composition, personages and actions, foreign to each other, an injudicious author loses that communication of emotions, by which alone he can intereft the heart, and raise the passions to their proper height and period. The full explication of this principle and all its consequences would lead us inco reasonings too profound and too copious for this enquiry. Tis fufficient, at present, to have established this conclusion, that the three éonnecting principles of all ideas are the relations of Refemblance, Contiguity, and Caufation.

S E C T I O N IV. SCEPTICAL DOUBTS CONCERNING THE OPERATIONS OF THE UNDERSTANDING.

P A R T 1. A LL the objects of human reason or enquiry may naturally be divided into

A two kinds, viz. Relations of Ideas and Matters of Fax. Of the first kind are the Tciences of Geometry, Algebra, and Arithmetic ; and in short, every affirmation, which is either intuitively or demonstratively certain. That the square of the byporbena fe is equal to the squares of the two sides, is a proposition, which expresses. a relation between these figures. That three times five is equal to the half of thirty, expreffes a relation between these numbers. Propositions of this kind are difcoverable by the mere operation of thought; without dependance on what is any where existent in the univerfe. Tho' there never were a true circle or triangle in nature, the truths demonstrated by EUCLID, would for ever retain their certainty and evidence.

MATTERS of faét, which are the fecond objects of human reason, are not ascertained in the same manner ; nor is our evidence of their truth, however great, of a like nature with the foregoing. The contrary of every matter of fact is still poffible; because it can never imply a contradiction, and is conceived by the mind with equal facility and distinctnefs, as if ever fo conformable to reality. Tbat the fan will not rise to-morraw is no lefs intelligible á proposition, and implies no more contradiction, than the affirmation, that it will rise. We should in vain, therefore, attempt to demonstrate its falfhood. Were. it demonstratively false, it

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would imply a contradi&ion, and could never be distinctly conceived by the mind.

It may, therefore, be a subject, orthy curiosity, to enquire what is the nature of that evidence, which assures us of any real existence and matter of fact, beyond the present testimony of our senses, or the records of our memory. This part of philosophy, 'tis observable, has been little cultivated, either by the ancients or moderns; and therefore our doubts and errors, in the prosecution of lo important an enquiry, may be the more excusable, while we march thro' such difficult parls, without any guide or direction. They may even prove useful, by exciting cule riosity, and destroying that implicit faith and security, which is the bane of all reasoning and free enquiry. The discovery of defects in the common philosophy, if any such there be, will not, I presume, “be a discouragement, but rather an incitement, as is usual, to attempt something more full and satisfactory, than has yet been proposed to the public.

. ALL reasonings concerning matter of fact seem to be founded in the relation of Cause and Effect. By means of that relation alone can we go beyond the evidence of our memory and senses. If you were to ask a man, why he believes any matter of fact, which is absent; for instance, that his friend is in the country, or in FRANCE ; he would give you a reason; and this reason would be some other fact; as a letter received from him, or the knowlege of his former resolutions and promises. A man, finding a watch or any other machine in a desert island, would conclude, that there had once been men in that island. All our reasonings concerning fact are of the same nature. And here 'tis constantly supposed, that there is a connexion between the present fact and that inferred from it. Were there nothing to bind them together, the inference would be entirely precarious. The hearing of an articulate voice and rational discourse in the dark assures us of the presence of some person': Why? because these are the effects of the human make and fabric, and closely connected with it. If we anatomize all the other reason. ings of this nature, we shall find, that they are founded in the relation of cause and effect, and that this, relation is either near, or remote, direct or collateral. Heat and light are collateral effects of fire, and the one 'effect may justly be inferred from the other..

If we would satisfy ourselves, therefore, concerning the nature of that evidence, , which assures us of all matters of fact, we must'enquire how we arrive at the knowlege of cause and effect.

I SHALL venture to affirm, as a general proposition, which admits of no exception, that the knowlege of this relation is not, in any instance, attained by reason- ings à priori ; but arises entirely from experience, when we find, that any particu

Jar objects are constantly conjoined with each other. Let an object be presented to, a man of ever so strong natural reason and abilities; if that object be entirely . new to him, he will not be able, by the most accurate examination of its sensible qualities, to discover any of its caules or effects. ADAM, tho' his rational faculties be supposed, at the very first, entirely perfect, could not have inferred from the Auidity, and transparency of water, that it would suffocate him, or from the light and warmth of fire, that it would consume him. No object ever discovers, by the qualities which appear to the senses, either the causes, which produced it, or

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the effects, which will arise from it; nor can our reason, unassisted by experience, ever draw any inferences concerning real existence and matter of fact.

This proposition, that causes and effects are discoverable, not by reason but by experience, will readily be admitted with regard to such objects, as we remember to have been once altogether unknown to us; since we must be conscious of the utter inability which we then lay under of foretelling what would arise from them. Present two smooth pieces of marble to a man, who has no tincture of natural philosophy; he will never discover, that they will adhere together, in fuch a manner as to require great force to separate them in a direct line, while they make so small resistance to a lateral pressure. Such events, as bear little analogy to the common course of nature, are also readily confessed to be known only by experience; nor does any man imagine that the explosion of gunpowder, or the attraction of a loadstone could ever be discovered by arguments à priori. In like manner, when an effect is supposed to depend upon an intricate machinery or secret structure of parts, we make no difficulty to attribute all our knowlege of it to experience. Who will assert, that he can give the ultimate reason, why milk or bread is proper nourishment for a man, not for a lion or a tyger !

But the same truth may not appear, at first sight, to have the same evidence with regard to events, which have become familiar to us from our first appearance in the world, which bear a close analogy to the whole course of nature, and which are supposed to depend on the simple qualities of objects, without any secret structure of parts. We are apt to imagine, that we could discover these effects, by the mere operations of our reason, without experience. We fancy, that, were we brought, on a sudden, into this world, we could at first have inferred, that one Billiard-ball would communicate motion to another upon impulse ; and that we needed not to have waited for the event, in order to pronounce with certainty concerning it. Such is the influence of custom, that, where it is strongest, it not only covers our natural ignorance, but even conceals itself, and feems not to take place, merely because it is found in the highest degree.

But to convince us, that all the laws of nature and all the operations of bodies, without exception, are known only by experience, the following reflections may, perhaps, fuffice. Were any object presented to us, and were we required to pronounce concerning the effect, which will result from it, without consulting past observation ; after what manner, I beseech you, must the mind proceed in this operation ? It must invent or imagine fome event, which it aferibes to the object as its effect; and 'tis plain that this invention must be entirely arbitrary. The mind can never possibly find the effect in the supposed caufë, by the most accurate scrutiny and examination. For the effect is totally different from the caufe, and consequently can never be discovered in it. Motion in the second Billiard-ball is a quite diftinct event from motion in the first ; nor is there any thing in the one to suggest the smallest hint of the other. A stone or piece of metal raised into the air, and left without any support, immediately falls: But to consider the matter à priori; is there any thing we discover in this situation, which can beger: the idea of a downward, rather than an upward, or any other motion, in the stone or metal?

AND as the first imagination or invention of a particular effect, in all natural operations, is arbitrary, where we consult not experience; so must we also efteem

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S ĆE PTICAL DOUBT S.

301 the supposed tye or connexion between the cause and effect, which binds them together, and renders it impossible, that any other effect could result from the operation of that cause. When I see, for instance, a Billiard-ball moving in a strait line towards another ; even suppose motion in the second ball should by accident be suggested to me, as the result of their contact or impulse; may I not conceive, that a hundred different events might as well follow from that cause? May not both these balls remain at absolute rest? May not the first ball return in a strait line, or leap of from the second in any line or direction ? All these suppositions are consistent and conceivable. Why then should we give the preference to one, which is no more consistent nor conceivable than the rest? All our reasonings à priori will never be able to shew us any foundation for this preference.

In a word, then, every effect is a distinct event from its cause. It could not, therefore, be discovered in the cause, and the first invention or conception of it, à priori, must be entirely arbitrary. And even after it is suggested, the conjunction of it with the cause must appear equally arbitrary ; since there are always many other effects, which, to reason, must seem fully as consistent 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 racional and modest, has ever pretended to align the ultimate cause of any natural operation, or to show distinctly 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 simplicity, and to resolve the many particular effects into a few general caufes, by means of reasonings from analogy, experience, and observation. But as to the causes of these general causes, we thould in vain attempt their discovery ; nor shall we ever be able to satisfy ourselves, by any particular explicacion of them. These ultimate Springs and principles are totally shut up from human curiosity and enquiry. Elafticity, 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 philofophy of the natural kind only staves off our ignorance a little longer : As perhaps the moft 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 spite of our endeavors to elude, or avoid it.

Nor is geometry, when taken into the assistance of natural philofophy, ever able to remedy this defce, 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 hy nature in her operations; and abstract reasonings are employed, either to assist experience in the discovery of these laws, or to determine their influence in particular instances, where it depends upon any precise degrees of distance and quantity. Thus ’ris a law of motion, discovered by experience, that the moment or force of any body in inotion is in the compound ratio or proportion of its folid contents and its velocity; and consequently, that a small force may remove the greatest ob

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stacle or raise the greatest weight, if by any contrivance or machinery we can encrease the velocity of that force, so as to make it an overmatch for its antagonist. Geometry affifts 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 à 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, new us the inseparable and inviolable connection between them. A man must be very sagaci. ous, 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 qualities.

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PART II.

But we have not, as yet, attained any tolerable fatisfaction with regard to. the question first proposed. Each solution still gives rise to a new question as, difficult as the foregoing, and leads us on to farther enquiries. When it is asked, What is the nature of all our reasonings concerning matter of fact? 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 humor, and ask, What is the foundation of all our conclufions from experience this implies a new question, which may be of more difficult for lution and explication. Philosophers, that give themselves airs of superior wisdom and sufficiency, have a hard task, when they encounter persons of inquisitive dispositions, who push them from every corner, to which they retreat, and who are fure at last to bring them to fome dangerous dilemma. The best expedient to prevent this confusion, is to be modest in our pretensions; 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' myself, in this section, 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 endeavor, both to explain and to defend.

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 color, weight, and consistence of bread; but neither senses 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 inotion 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

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