In the versified declamation which then reigned on the French stage, nothing was left to natural action, nothing was told by change of position, by movement without speech, or in short by any means other than discourse.

Diderot, repudiating the conventions of dramatic art, and consulting nature or reality, saw that there are many scenes in life in which it is more natural to the personages of the scene to move than to speak, in which indeed motion is natural, and speech is altogether unnatural.

If this be so in real life, he said, it should be so on the stage, because nothing passes in the world which may not pass also in the theatre; and as pantomime, or expression of emotion, feeling, purpose, otherwise than by speech, has so much to do in life, the dramatist should make abundant use of pantomime in composing stage-plays.

Nor should he trust to the actor's invention and spontaneous sense of appropriateness.

He ought to write down the pantomime whenever it adds energy or clearness to the dialogue; when it binds the parts of the dialogue together; when it consists in a delicate play that is not easily divined; and almost always he ought to write it down in the opening of a scene.