In depicting these human follies, it is the office of the comic poet to imitate justice, to improve the moral life and purify language, and to stir up gentle affections.[518] The moving of mere laughter is not always the end of comedy; in fact, Jonson interprets Aristotle as asserting that the moving of laughter is a fault in comedy, a kind of turpitude that depraves a part of man's nature.[519] This conclusion is based on an interpretation of Aristotle which has persisted almost to the present day. In the _Poetics_, [Greek: to geloion], the ludicrous, is said to be the subject of comedy;[520] and many critics have thought that Aristotle intended by this to distinguish between the risible and the ridiculous, between mere laughter and laughter mixed with contempt or disapprobation.[521] The nature and the source of one of the most important elements in Jonson's theory of comedy, his doctrine of "humours," have been briefly discussed in the first section of this essay. It will suffice here to define a "humour" as an absorbing singularity of character,[522] and to note that it grew out of the conception of _decorum_ which played so important a part in poetic theory during the Italian Renaissance. III. _The Dramatic Unities_ Before leaving the theory of the drama, there is one further point to be discussed,--the doctrine of the unities. It has been seen that the unities of time and place were, in Italy, first formulated together by Castelvetro in 1570, and in France by Jean de la Taille in 1572. The first mention of the unities in England is to be found, a dozen years later, in the _Defence of Poesy_, and it cannot be doubted that Sidney derived them directly from Castelvetro. Sidney, in discussing the tragedy of _Gorboduc_, finds it "faulty in time and place, the two necessary companions of all corporal actions; for where the stage should always represent but one place, and the uttermost time presupposed in it should be, both by Aristotle's precept and common reason, but one day, there [_i.e._ in _Gorboduc_] is both many days and many places inartificially imagined."[523] He also objects to the confusions of the English stage, where on one side Africa and on the other Asia may be represented, and where in an hour a youth may grow from boyhood to old age.[524] How absurd this is, common sense, art, and ancient examples ought to teach the English playwright; and at this day, says Sidney, the ordinary players in Italy will not err in it. If indeed it be objected that one or two of the comedies of Plautus and Terence do not observe the unity of time, let us not follow them when they err but when they are right; it is no excuse for us to do wrong because Plautus on one occasion has done likewise.