It is scarcely necessary to say that there is little profit in a partnership for play-making when both of the associates are equally inexpert, or when they were both possessed of wrong notions about the art of the drama. In the former case we have the blind leading the blind, and the most lamentable example of this is the long forgotten 'Ah Sin,' which Bret Harte and Mark Twain combined to compose that C. T. Parsloe could impersonate the Heathen Chinee. In the latter case we have not only the blind leading the blind, but a perverseness in going the wrong way, intensified by the complete sympathy between the two associates; and the most lamentable example of this is the 'Deacon Brodie' of Robert Louis Stevenson and William Ernest Henley, who not only were ignorant of the modern technic of the drama, but who ignored it of set purpose, deliberately going up a blind alley despite the plain sign that there was no thorofare. III Yet Stevenson, at least, perceived clearly enough what ought to be the more evident advantages of collaboration, that it focused "two minds together on the stuff," thus producing "an extraordinarily greater richness of purview, consideration, and invention." Collaboration will probably always produce a greater richness of invention, since each of the partners is likely to stimulate the other, their two minds striking sparks like flint and steel. But it can produce a greater richness of consideration only when each is willing both to yield and to oppose. Neither must yield too easily; each of them must stand out for his own suggestions; and each of them must insist on weighing and measuring the suggestions of his ally. If they are too sympathetic, if their two hearts beat as one, then the advantage of their having two heads is diminished. If the two partners always think alike, then there will be no greater richness of purview.