The distinction I am aiming to draw can perhaps be illustrated by comparing a precis of a book with a trailer of a film. The precis represents the conventional method of pre paring the speech. The film trailer represents, albeit to an exaggerated degree, the approach I am advocating. It reveals the subject matter and the mood and style of the film. It selects certain details without attempting to precis the story. It is assembled in an interesting way and it raises interest in the film that it is encouraging the viewer to watch.