On the other hand, the drama is a rigid form, limited to the two hours' traffic of the stage. Just as the decorative artist has to fill the space assigned to him and must respect the dispositions of the architect, so the playwright must work his will within the requirements of the theater, turning to advantage the restrictions which he should not evade. He must always appeal to the eye as well as to the ear, never forgetting that the drama, while it is in one aspect a department of literature, in another is a branch of the show-business. He must devise stage-settings at once novel, ingenious and plausible; and he must invent reasons for bringing together naturally the personages of his play in the single place where each of his acts passes. He must set his characters firm on their feet, each speaking for himself and revealing himself as he speaks; for they need to have internal vitality as they cannot be painted from the outside. He must see his creatures as well as hear them; and he must know always what they are doing and how they are looking when they are speaking. He cannot comment on them or explain them, or palliate their misdeeds. He must project them outside of himself; and he cannot be his own lecturer to point out their motives. He must get on without any attempt to point out the morality of his work, which remains implicit altho it ought to be obvious. He must work easily within many bonds, seeming always to be free and unhampered; and he must turn to account these restrictions and find his profit in them, for they are the very qualities which differentiate the drama and make it what it is. This essential unlikeness of the drama to the novel is so keenly appreciated by every novelist who happens also to be a dramatist, that he is rarely tempted to treat the same theme in both forms, feeling instinctively that it belongs either to the stage or to the library. Often, of course, he writes a novel rather than a play, because he knows that a certain theme, adequate as it may be for a novel, lacks that essential struggle, that naked assertion of the human will, that clash of contending desires, which must be visible in a play if this is to sustain the interest of an audience. Many a tale, pleasing to thousands of readers because it abounds in brisk adventure, will not lend itself to successful dramatization because its many episodes are not related to a single straight-forward conflict of forces.