The essentials of the manner of poetry being language metrical and imaginative, the essential of the matter is that it be the expression of passionate emotion. By passionate emotion is meant any feeling, powerful or delicate, which is capable of filling the whole soul; of taking possession for the time being of the entire man. It may be fierce hate, enthralling love, ambition, lust, rage, jealousy, joy, sorrow, any over-mastering mood, or it may be one of those intangible inclinations, those moods of mist, ethereal as hazes in October, those caprices of pleasure or sadness which Tennyson had the art so marvelously to reproduce. Passionate emotion is by no means necessarily intense, but it is engrossing. For the time being, at least, it seems to absorb the whole inner consciousness. It is the completeness with which such a mood takes possession of the mind, so that for the moment it is to all intents and purposes the man himself, that gives it so great an importance in human life and makes it the fitting and the sole essential theme of the highest art. Behind all serious human effort lies the instinctive sense of the fitness of things. The artist must always convince that his end is worthy of the means which he employs to reach it; and it follows naturally that the writer who uses imaginative diction and the elaborateness of metre must justify this by what he embodies in them. Metrical forms are as much out of place in treating of the material concerns of life as would be court robes or religious rites in the reaping of a field or the selling of a cargo of wool. The poet is justified in his use of all the resources of form and of poetic diction by the fact that the message which he is endeavoring to convey is high and noble; that the meaning which he attempts to impart is so profoundly subtle as to be inexpressible unless the words which he employs are assisted by the language of rhythm and metre.