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 reasonings concerning matter of fact seem 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 ak a man, why he believes any matter of fact, which is abfent; for instance, that his friend is in the country, or in FRANCE; he would give you a reason; and this reafon would be fome other fact; as a letter received from him, or the knowlege of his former refolutions and promifes. A man, finding a watch or any other machine in a defart ifland, would conclude, that there had once been men in that island. All our reafonings concerning fact are of the fame nature. And here 'tis constantly supposed, 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 dif courfe in the dark affures us of the prefence of fome perfon: Why? because these are the effects of the human make and fabric, and clofely connected with it. If we anatomize all the other reasonings of this nature, we shall find, that they are founded in the

relation

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 caufe 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 inftance, attained by reasonings à priori; but arifes entirely from experience, when we find, that any particular objects are conftantly conjoined with each other. Let an object be prefented to a man of ever fo ftrong natural reason and abilities; if that object be entirely new to him, he will not be able, by the most accurate examination of its fenfible qualities, to difcover any of its caufes or effects. ADAM, tho' his rational faculties be fuppofed, at the very firft, entirely perfect, could not have inferred from the fluidity and tranfparency of water, that it would fuffocate him, or from the light and warmth of fire, that it would confume him. No object ever difcovers, by the qualities which appear to the fenfes, either the causes, which produced it, or the effects, which will arife from it; nor can our reafon, unaf

fifted 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 arife from them. Present two smooth pieces of marble to a man, who has no tincture of natural philosophy; 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 refistance 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 fuppofed to depend upon an intricate machinery or secret structure of parts, we make no difficulty to attribute all our knowlege of it to experi ence. 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 the fame truth may not appear, at first fight, to have the fame evidence with regard to events, VOL. III. which

D

which have become familiar to us from our firft appearance in the world, which bear a close analogy to the whole courfe of nature, and which are fuppofed to depend on the fimple qualities of objects, without any fecret ftructure of parts. We are apt to imagine, that we could discover 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 firft 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 ftrongeft, 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 prefented to us, and were we required to pronounce concerning the effect, which will refult from it, without confulting past observation; after what manner, I befeech 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 fuppofed caufe, by the most accurate fcrutiny and examination. For the effect is totally different from the caufe, and confequently can never be discovered in it. Motion in the fecond Billiard-ball is a quite diftinct event from motion in the first ; nor is there any thing in the one to fuggeft the fmalleft hint of the other. A ftone or piece of metal raised into the air, and left without any fupport, immediately falls: But to confider the matter à priori, is there any thing we discover 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 efteem 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 caufe. When I fee, for inftance, a Billiard-ball moving in a strait line towards another; even fuppofe motion in the fecond ball fhould by accident be fuggefted to me, as the refult of their contact or impulfe; 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 ftrait line, or leap off from the fecond in any line or direction?