when they are tranquil and cool, and such strokes come by an unexpected inspiration.[275] It is for coolness to temper the delirium of enthusiasm.  It is not the violent man who is beside himself that disposes of us; that is an advantage reserved for the man who possesses himself.  The great poets, the great actors, and perhaps generally all the great imitators of nature, whatever they may be, are gifted with a fine imagination, a great judgment, a subtle tact, a sure taste, but they are creatures of the smallest sensibility.  They are equally well fitted for too many things; they are too busy in looking, in recognising, and in imitating, to be violently affected within themselves.  Sensibility is hardly the quality of a great genius.  He will have justice; but he will practise it without reaping all the sweetness of it.  It is not his heart, but his head, that does it all.  Well, then, what I insist upon, says Diderot, is that it is extreme sensibility that makes mediocre actors; it is mediocre sensibility that makes bad actors; and it is the absolute want of sensibility that prepares actors who shall be sublime.[276]

This is worked out with great clearness and decision, and some of the illustrations to which he resorts to lighten the dialogue are amusing enough.  Perhaps the most interesting to us English is his account of Garrick, whose acquaintance he made towards the year 1765.  He says that he saw Garrick pass his head between two folding doors, and in the space of a few seconds, his face went successively from mad joy to moderate joy, from that to tranquillity, from tranquillity to surprise, from surprise to astonishment, from astonishment to gloom, from gloom to utter dejection, from dejection to fear, from fear to horror, from horror to despair, and then reascend from this lowest degree to the point whence he had started.[277]

Of course his soul felt none of these emotions.  “If you asked this famous man, who by himself was as well worth a journey to England to see, as all the wonders of Rome are worth a journey to Italy, if you asked him, I say, for the scene of The Little Baker’s Boy, he played it; if you asked him the next minute for the scene from Hamlet, he played that too for you, equally ready to sob over the fall of his pies, and to follow the path of the dagger in the air."[278]

Apart from the central proposition, Diderot makes a number of excellent observations which show his critical faculty at its best.  As, for example, in answering the question, what is the truth of the stage?  Is it to show things exactly as they are in nature?  By no means.  The true in that sense would only be the common.  The really true is the conformity of action, speech, countenance, voice, movement, gesture, with an ideal model imagined by the poet, and often exaggerated by the player.  And the marvel is that this model influences not only the tone, but the whole carriage and gait.  Again, what is the aim of multiplied rehearsals?  To