fible; because it can never imply a contradiction, and is conceived by the mind with equal facility and diftin&ness, as if ever so conformable to reality. That the fun will not rife tomorrow is no less intelligible a propofition, and implies no more. contradiction, than the affirmation, that it will rife. We fhould in vain, therefore, attempt to demonftrate its falfhood. Were it demonstratively false, it would imply a contradiction,, and could never be distinctly conceived by the mind. ̧

It may, therefore, be a fubject worthy curiofity, to enquire what is the nature of that evidence, which affures us of any real existence and matter of fact, beyond the prefent teftimony of our fenfes, or the records of our memory. This part of philofophy, 'tis obfervable, has been little cultivated, either by the antients or moderns; and therefore our doubts and errors, in the prosecution of fo important an enquiry, may be the more excufable, while we march through such difficult paths, without any guide or direction. They may even prove useful, by exciting curiosity, and destroying that implicit faith and security, which is the bane of all reafoning and free enquiry. The difcovery of defects in the common philofophy, if any fuch there be, will not, I prefume, be a difcouragement, but rather an incitement, as is ufual, to attempt fomething more full and fatisfactory, than has yet been propofed to the public.

All reafonings concerning matter of fact feem to be founded in the relation of Caufe and Effect. By means of that relation alone can we go beyond the evidence of our memory and fenfes. If you were to ask a man, why he believes any matter of fact, which is abfent; for inftance, that his friend is in the country, or in FRANCE; he would give you a reason; and this reason would be fome 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 defart island, would conclude, that there had once been men in that island. All our reafonings concerning fact are of the fame nature. And here 'tis conftantly fuppofed, that there is a connexion between the prefent 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 difcourfe in the dark affures us of the prefence of fome perfon: Why? because these are effects of the human make and fabric, and closely connected with it. If we anatomize all the other reasonings 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 juftly be inferred from the other.

If we would fatisfy ourselves, therefore, concerning the nature of that evidence, which affures 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 propofition, which admits of no exception, that the knowlege of this relation is not, in any inftance, attained by reasonings à priori; but arifes entirely from experience, when we find, that any particular objects are constantly conjoined with each other. Let an object be presented to a man of ever fo ftrong natural reafon and abilities; if that object be entirely new to him, he will not be able, by the moft accurate examination of its fenfible qualities, to discover any of its caufes or effects. ADAM, though his

rational

rational faculties be supposed, at the very first, entirely perfect, could not have inferred from the fluidity and transparency of water, that it would fuffocate him, or from the light and warmth of fire, that it would confume him. No object ever discovers, by the qualities which appear to the senses, either the causes which produced it, or the effects, which will arife from it; nor can our reason, unaffifted by experience, ever draw any inferences concerning real existence and matter of fact.

This propofition, that causes and effects are difcoverable, not by reafon but by experience, will readily be admitted with regard to fuch objects, as we remember to have been once altogether unknown to us; fince 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 philofophy; he will never difcover that they will adhere together, in such a manner as to require great force to separate them in a direct line, while they' make so small a resistance to a lateral preffure. Such events, as bear little analogy to the common course of nature, are also readily confeffed 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 difcovered 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 affert, 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

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But the fame truth may not appear, at first sight, to have the fame 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 fimple qualities of objects, without any secret structure of parts. We are apt to imagine, that we could difcover these effects by the mere operations of our reafon, 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 cuftom, that, where it is strongest, it not only covers our natural ignorance, but even conceals itself, and seems 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 prefented to us, and were we required to pronounce concerning the effect, which will refult from it, without confulting past obfervation; after what manner, I beseech I beseech you, muft the mind proceed in this operation? It must invent or imagine fome event, which it ascribes to the object as its effect; and 'tis plain that this invention must be entirely arbitrary. The mind can never poffibly find the effect in the suppofed cause, by the most accurate fcrutiny and examination. For the effect is totally different from the cause, and consequently can never be discovered in it. Motion in the fecond billiard-ball is a quite diftinct event from motion in the first

nor

nor is there any thing in the one to fuggeft the smallest hint of the other. A ftone or piece of metal raised into the air, and left without any support, immediately falls: But to confider the matter à priori, is there any thing we difcover in this fituation, which can beget the idea of a downward, rather than an upward, or any other motion, in the ftone or metal?

And as the first imagination or invention of a particular effect, in all natural operations, is arbitrary, where we confult not experience; fo must we also esteem the supposed tye or connexion between the cause and effect, which binds them together, and renders it impoffible, that any other effect could refult from the operation of that cause. When I fee, for instance, a billiard-ball moving in a strait line towards another; even suppose motion in the second ball fhould 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 caufe? May not both these balls remain at abfolute reft? May not the first ball return in a strait line, or leap off from the second in any line or direction? All these fuppofitions are confiftent and conceivable. Why then should we give the preference to one, which is no more confiftent nor conceivable than the reft? All our reasonings à priori will never be able to fhew us any foundation for this preference.

In a word, then, every effect is a diftinct 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 fuggefted, the conjunction of it with the cause must appear equally arbitrary; fince there are always

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