So the arts have a common end, and entirely different means. Hence the general rules common to all, and particular rules for each. I have neither time nor space to enter into details on this point. I limit myself to repeating, that the great law which governs all others, is expression. Every work of art that does not express an idea signifies nothing; in addressing itself to such or such a sense, it must penetrate to the mind, to the soul, and bear thither a thought, a sentiment capable of touching or elevating it. From this fundamental rule all the others are derived; for example, that which is continually and justly recommended,--composition. To this is particularly applied the precept of unity and variety. But, in saying this, we have said nothing so long as we have not determined the nature of the unity of which we would speak. True unity, is unity of expression, and variety is made only to spread over the entire work the idea or the single sentiment that it should express. It is useless to remark, that between composition thus defined, and what is often called composition, as the symmetry and arrangement of parts according to artificial rules, there is an abyss. True composition is nothing else than the most powerful means of expression. Expression not only furnishes the general rules of art, it also gives the principle that allows of their classification. In fact, every classification, supposes a principle that serves as a common measure. Such a principle has been sought in pleasure, and the first of arts has seemed that which gives the most vivid joys. But we have proved that the object of art is not pleasure:--the more or less of pleasure that an art procures cannot, then, be the true measure of its value. This measure is nothing else than expression. Expression being the supreme end, the art that most nearly approaches it is the first of all. All true arts are expressive, but they are diversely so. Take music; it is without contradiction the most penetrating, the profoundest, the most intimate art. There is physically and morally between a sound and the soul a marvellous relation. It seems as though the soul were an echo in which the sound takes a new power. Extraordinary things are recounted of the ancient music. And it must not be believed that the greatness of effect supposes here very complicated means. No, the less noise music makes, the more it touches. Give some notes to Pergolese, give him especially some pure and sweet voices, and he returns a celestial charm, bears you away into infinite spaces, plunges you into ineffable reveries. The peculiar power of music is to open to the imagination a limitless career, to lend itself with astonishing facility to all the moods of each one, to arouse or calm, with the sounds of the simplest melody, our accustomed sentiments, our favorite affections. In this respect music is an art without a rival:--however, it is not the first of arts.