which unites them into one body, is the relation of caufe and effect, the fame which takes place in epic poetry; and that, in the latter compofition, this connexion is only required to be clofer and more fenfible, on account of the lively imagination and ftrong paffions, which must be touched by the poet in his narration. The PELOPONNESIAN war is a proper fubject for history, the fiege of ATHENS for an epic poem, and the death of ALCIBIADES for a tragedy.

As the difference, therefore, between hiftory and epic poetry confifts only in the degrees of connexion, which bind together those several events, of which their subject is compofed, it will be difficult, if not impoffible, by words, to determine exactly the bounds, which separate them from each other. That is a matter of tafte more than of reasoning; and perhaps, this unity may often be discovered in a fubject, where, at first view, and from an abftract confideration, we fhould leaft expect to

find it.

It is evident, that HOMER, in the courfe of his narration, exceeds the firft propofition of his fubject; and that the anger of ACHILLES, which caufed the death of HECTOR, is not the fame with that which produced fo many ills to the GREEKS. But the ftrong connexion between these two movements, the quick tranfition from one to another, the contraft* between the effects of concord and difcord among the princes, and the natural curiofity which we have to fee ACHILLES in action, after

Contraft or contrariety is a connexion among ideas, which may, perhaps, be confidered as a mixture of caufation and refemblance. Where two objects are contrary, the one deftroys the other, i, e. is the caufe of its annihilation, and the idea of the annihilation of an object implies the idea of its former exifience,

fo

fo long a repofe; all thefe caufes carry on the reader, and produce a fufficient unity in the subject.

It may be objected to MILTON, that he has traced up his causes to too great a distance, and that the rebellion of the angels produces the fall of man by a train of events, which is both very long and very cafual. Not to mention, that the creation of the world, which he has related at length, is no more the cause of that catastrophe, than of the battle of PHARSALIA, or any other event, that has ever happened. But if we consider, on the other hand, that all thefe events, the rebellion of the angels, the creation of the world, and the fall of man, refemble each other, in being miraculous and out of the common course of nature; that they are fuppofed to be contiguous in time; and that being detached from al other events, and being the only original facts, which revelation difcovers, they ftrike the eye at once, and naturally recall each other to the thought or imagination: If we confider all thefe circumftances, I fay, we fhall find, that these parts of the action have a fufficient unity to make them be comprehended in one fable or narration. To which we may add, that the rebellion of the angels and the fall of man have a peculiar refemblance, as being counterparts to each other, and prefenting to the reader the fame moral, of obedience to our Creator.

Thefe loose hints I have thrown together, in order to excite the curiofity of philofophers, and beget a fufpicion at least, if not a full persuasion, that this subject is very copious, and that many operations of the human mind depend on the connexion or affociation of ideas, which is here explained. Particularly, the fympathy between the paffions and imagination will, perhaps, + appear remarkable; while we obferve that the affections,

excited

excited by one object, pass easily to another object connected with it; but transfufe themfelves with difficulty, or not at all, along different objects, which have no manner of connexion together. By introducing, into any compofition, perfonages and actions, foreign to each other, an injudicious author lofes that communication of emotions, by which alone he can intereft the heart, and raise the paffions to their proper height and period. The full explication of this principle and all its confequences would lead us into reafonings too profound and too copious for this enquiry. It is fufficient, at present, to have established this conclufion, that the three connecting principles of all ideas are the relations of Refemblance, Contiguity, and Caufation.

SECTION IV.

SCEPTICAL DOUBTS concerning the OPERATIONS of the UNDERSTANDING.

A

PARTI.

LL the objects of human reafon or enquiry may naturally be divided into two kinds, viz. Relations of Ideas and Matters of Fact. Of the first kind are the sciences of Geometry, Algebra, and Arithmetic; and in fhort, every affirmation, which is either intuitively or demonstratively certain. That the fquare of the hypothenufe is equal to the fquare of the two fides, is a propofition, which expreffes a relation between these figures. That three times five is equal to the half of thirty, expreffes a relation between these numbers. Propofitions of this kind are discoverable by the mere operation of thought, without dependence on what is any where existent in the universe. Though there never were a circle or triangle in nature, the truths, demonftrated by EUCLID, would for ever retain their certainty and evidence.

Matters of fact, which are the fecond objects of human reason, are not afcertained in the fame 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 the fame facility and diftinctnefs, as if ever fo conform

R