In art, interest must be centred on the principal theme. Drama is the most difficult of all arts. In it two things are to be satisfied—first, the ears, and second, the eyes. To paint a scene, if one thing be painted, it is easy enough; but to paint different things and yet to keep up the central interest is very difficult. Another difficult thing is stage-management, that is, combining different things in such a manner as to keep the central interest intact.