[Headnote to follow.]
Nunquam aliud natura, aliud sapientia dicit.
For wisdom ever echoes nature's voice.
 Every government, say the politicians, is perpetually degenerating towards corruption, from which it must be rescued at certain periods by the resuscitation of its first principles, and the re-establishment of its original constitution. Every animal body, according to the methodick physicians, is, by the predominance of some exuberant quality, continually declining towards disease and death, which must be obviated by a seasonable reduction of the peccant humour to the just equipoise which health requires.
 In the same manner the studies of mankind, all at least which, not being subject to rigorous demonstration, admit the influence of fancy and caprice, are perpetually tending to error and confusion. Of the great principles of truth which the first speculatists discovered, the simplicity is embarrassed by ambitious additions, or the evidence obscured by inaccurate argumentation; and as they descend from one succession of writers to another, like light transmitted from room to room, they lose their strength and splendour, and fade at last in total evanescence.
 The systems of learning therefore must be sometimes reviewed, complications analised into principles, and knowledge disentangled from opinion. It is not always possible, without a close inspection, to separate the genuine shoots of consequential reasoning, which grow out of some radical postulate, from the branches which art has engrafted on it. The accidental prescriptions of authority, when time has procured them veneration, are often confounded with the laws of nature, and those rules are supposed coeval with reason, of which the first rise cannot be discovered.
 Criticism has sometimes permitted fancy to dictate the laws by which fancy ought to be restrained, and fallacy to perplex the principles by which fallacy is to be detected; her super-intendance of others has betrayed her to negligence of herself; and, like the antient Scythians, by extending her conquests over distant regions, she has left her throne vacant to her slaves.
 Among the laws of which the desire of extending authority, or ardour of promoting knowledge has prompted the prescription, all which writers have received, had not the same original right to our regard. Some are to be considered as fundamental and indispensable, others only as useful and convenient; some as dictated by reason and necessity, others as enacted by despotick antiquity; some as invincibly supported by their conformity to the order of nature and operations of the intellect; others as formed by accident, or instituted by example, and therefore always liable to dispute and alteration.
 That many rules have been advanced without consulting nature or reason, we cannot but suspect, when we find it peremptorily decreed by the antient masters, that "only three speaking personages should appear at once upon the stage"; a law which, as the variety and intricacy of modern plays has made it impossible to be observed, we now violate without scruple, and, as experience proves, without inconvenience.
 The original of this precept was merely accidental. Tragedy was a monody or solitary song in honour of Bacchus, improved afterwards into a dialogue by the addition of another speaker; but the antients, remembering that the tragedy was at first pronounced only by one, durst not for some time venture beyond two; at last when custom and impunity had made them daring, they extended their liberty to the admission of three, but restrained themselves by a critical edict from further exorbitance.
 By what accident the number of acts was limited to five, I know not that any author has informed us; but certainly it is not determined by any necessity arising either from the nature of action or propriety of exhibition. An act is only the representation of such a part of the business of the play as proceeds in an unbroken tenor, or without any intermediate pause. Nothing is more evident than that of every real, and by consequence of every dramatick action, the intervals may be more or fewer than five; and indeed the rule is upon the English stage every day broken in effect, without any other mischief than that which arises from an absurd endeavour to observe it in appearance. Whenever the scene is shifted the act ceases, since some time is necessarily supposed to elapse while the personages of the drama change their place.
 With no greater right to our obedience have the criticks confined the dramatic action to a certain number of hours. Probability requires that the time of action should approach somewhat nearly to that of exhibition, and those plays will always be thought most happily conducted which croud the greatest variety into the least space. But since it will frequently happen that some delusion must be admitted, I know not where the limits of imagination can be fixed. It is rarely observed that minds not prepossessed by mechanical criticism feel any offence from the extension of the intervals between the acts; nor can I conceive it absurd or impossible, that he who can multiply three hours into twelve or twenty-four, might image with equal ease a greater number.
 I know not whether he that professes to regard no other laws than those of nature, will not be inclined to receive tragi-comedy to his protection, whom, however generally condemned, her own laurels have hitherto shaded from the fulminations of criticism. For what is there in the mingled drama which impartial reason can condemn? The connexion of important with trivial incidents, since it is not only common but perpetual in the world, may surely be allowed upon the stage, which pretends only to be the mirrour of life. The impropriety of suppressing passions before we have raised them to the intended agitation, and of diverting the expectation from an event which we keep suspended only to raise it, may be speciously urged. But will not experience shew this objection to be rather subtle than just? is it not certain that the tragic and comic affections have been moved alternately with equal force, and that no plays have oftner filled the eye with tears, and the breast with palpitation, than those which are variegated with interludes of mirth?
 I do not however think it safe to judge of works of genius merely by the event. These resistless vicissitudes of the heart, this alternate prevalence of merriment and solemnity, may sometimes be more properly ascribed to the vigour of the writer than the justness of the design: and instead of vindicating tragi-comedy by the success of Shakespear, we ought perhaps to pay new honours to that transcendent and unbounded genius that could preside over the passions in sport; who, to actuate the affections, needed not the slow gradation of common means, but could fill the heart with instantaneous jollity or sorrow, and vary our disposition as he changed his scenes. Perhaps the effects even of Shakespeare's poetry might have been yet greater, had he not counter-acted himself; and we might have been more interested in the distresses of his heroes had we not been so frequently diverted by the jokes of his buffoons.
 There are other rules more fixed and obligatory. It is necessary that of every play the chief action should be single; for since a play represents some transaction, through its regular maturation to its final event, two actions equally important must evidently constitute two plays.
 As the design of tragedy is to instruct by moving the passions, it must always have a hero, a personage apparently and incontestably superior to the rest, upon whom the attention may be fixed, and the anxiety suspended. For though of two persons opposing each other with equal abilities and equal virtue, the auditor will inevitably in time choose his favourite, yet as that choice must be without any cogency of conviction, the hopes or fears which it raises will be faint and languid. Of two heroes acting in confederacy against a common enemy, the virtues or dangers will give little emotion, because each claims our concern with the same right, and the heart lies at rest between equal motives.
 It ought to be the first endeavour of a writer to distinguish nature from custom, or that which is established because it is right, from that which is right only because it is established; that he may neither violate essential principles by a desire of novelty, nor debar himself from the attainment of beauties within his view by a needless fear of breaking rules which no literary dictator had authority to enact.