The dictum of Aristotle in reference to metre in poetry related only to epic and dramatic verse, for what we understand as lyric poetry was separated by the Greeks as song in which of course metre is compulsory. It is doubtful whether a single definition can cover both epic poetry, whose beauty lies almost wholly in the substance, and lyric verse where the beauty rests chiefly in qualities of expression and musical form, and in which indeed the substance may be altogether negligible. A cursory examination of Watts-Dunton's definition of "Poetry," which is admittedly the best put forward in recent times, shows its entire inadequacy. "Absolute poetry," he says, "is the concrete and artistic expression of the human mind in emotional and rhythmical language."[a] This would exclude from the art some of the finest sacred verse, which, though in the form of prose, has been recognized as poetry from time immemorial. Metre is only one of the devices of the poet for accomplishing his end---the presentation of beautiful pictures upon the mind, but in high poetry there is a still more compulsory artifice which is not included in Watts-Dunton's definition, and that is metaphor. In the form of words the details of a picture can only be dealt with successively, and not simultaneously, and without metaphor the poet would sometimes be in the position of the painter who should present a dozen different pictures each containing only one part of a composition, and call upon the observer to put the pieces together in his mind. Further the term "absolute" in the definition quoted has no comprehensible meaning if it does not exclude a good deal of verse which is commonly recognized as poetry, while, as is admitted by Watts-Dunton, there is much accepted lyric verse without concrete expression. In high poetry as in high painting, the beauty appeals both to the senses and the mind, and in each art the quality descends as the sensorial overbalances the intellectual appeal, and the effect becomes more ephemeral. In the very highest of the plastic arts, colour has little value except in assisting definition; and in the very highest poetry musical form has only an emphasizing value, for the sensorial beauty arising from form in the one case, and form and action in the other, entirely overpowers the harmonies of colour and tone respectively. But colour without design is meaningless, so that it cannot be applied in the fine arts apart from design: hence in painting, colour presents no complication in respect of definition. On the other hand music, with or without association with poetry, is equally an art since in either case it imitates the effects of human emotions in a beautiful way. Thus, where metre is present poetry is a combined art, and seeing that metre may not be present, a definition of "Poetry" must cover what may be in one case a pure, and in another, a compound art. [a] Article on "Poetry," _Encyclopædia Britannica_, 11th edition. NOTE 21. PAGE 55