Again, though he may be right in contending that there is a serious kind of comedy as distinct from that gay comedy which is neighbour to farce--of this we shall see more presently--yet he is certainly wrong in believing that we can willingly endure five acts of serious comedy without a single relieving passage of humour. Contrast of character, where all the characters are realistic and common, is not enough. We crave contrast in the dramatic point of view. We seek occasional change of key. That serious comedy should move a sympathetic tear is reasonable enough; but it is hard to find that it grudges us a single smile. The result of Diderot's method is that the spectator or the reader speedily feels that what he has before him substitutes for dramatic fulness and variety the flat monotony of a homily or a tract. It would be hard to show that there is no true comedy without laughter--Terence's _Hecyra_, for instance--but Diderot certainly overlooked what Lessing and most other critics saw so clearly, that laughter rightly stirred is one of the most powerful agencies in directing the moral sympathies of the audience,--the very end that Diderot most anxiously sought. It is mere waste of time to bestow serious criticism on Diderot's two plays, or on the various sketches, outlines, and fragments of scenes with which he amused his very slight dramatic faculty. If we wish to study the masterpieces of French comedy in the eighteenth century, we shall promptly shut up the volumes of Diderot, and turn to the ease and soft gracefulness of Marivaux's _Game of Love and Chance_, to the forcible and concentrated sententiousness of Piron's _Metromanie_, to the salt and racy flavour of Le Sage's _Turcaret_. Gresset, again, and Destouches wrote at least two comedies that were really fit for the stage, and may be read with pleasure to-day. Neither of these compliments can fairly be paid to _The Natural Son_ and _The Father of the Family_. Diderot's plays ought to be looked upon merely as sketchy illustrations of a favourite theory; as the rough drawings on the black board with which a professor of the fine arts may accompany a lecture on oil painting.