It has always been our opinion, that the very essence of poetry--apart from the pathos, the wit, or the brilliant description which may be imbodied in it, but may exist equally in prose--consists in the fine perception and vivid expression of the subtle and mysterious analogy which exists between the physical and the moral world--which makes outward things and qualities the natural types and emblems of inward gifts and emotions, or leads us to ascribe life and sentiment to every thing that interests us in the aspects of external nature. The feeling of this analogy, obscure and inexplicable as the theory of it may be, is so deep and universal in our nature, that it has stamped itself on the ordinary language of men of every kindred and speech: that to such an extent, that one-half of the epithets by which we familiarly designate moral and physical qualities, are in reality so many metaphors, borrowed reciprocally, upon this analogy, from those opposite forms of expression. The very familiarity, however, of the expression, in these instances, takes away its political effect--and indeed, in substance, its metaphorical character. The original sense of the word is entirely forgotten in the derivative one to which it has succeeded; and it requires some etymological recollection to convince us that it was originally nothing else than a typical or analogical illustration. Thus we talk of a sparkling wit, and a furious blast--a weighty argument, and a gentle stream--without being at all aware that we are speaking in the language of poetry, and transferring qualities from one extremity of the sphere of being to another. In these cases, accordingly, the metaphor, by ceasing to be felt, in reality ceases to exist, and the analogy being no longer intimated, of course can produce no effect. But whenever it is intimated, it does produce an effect; and that effect we think is poetry.
It has substantially two functions, and operates in two directions. In the _first_ place, when material qualities are ascribed to mind, it strikes vividly out, and brings at once before us, the conception of an inward feeling or emotion, which it might otherwise have been difficult to convey, by the presentiment of some bodily form or quality, which is instantly felt to be its true representative, and enables us to fix and comprehend it with a force and clearness not otherwise attainable; and, in the _second_ place, it vivifies dead and inanimate matter with the attributes of living and sentient mind, and fills the whole visible universe around us with objects of interest and sympathy, by tinting them with the hues of life, and associating them with our own passions and affections. This magical operation the poet too performs, for the most part, in one of two ways--either by the direct agency of similies and metaphors, more or less condensed or developed, or by the mere graceful presentment of such visible objects on the scene of his passionate dialogues or adventures, as partake of the character of the emotion he wishes to excite, and thus form an appropriate accompaniment or preparation for its direct indulgence or display. The former of those methods has perhaps been most frequently employed, and certainly has most attracted attention. But the latter, though less obtrusive, and perhaps less frequently resorted to of set purpose, is, we are inclined to think, the most natural and efficacious of the two; and it is often adopted, we believe unconsciously, by poets of the highest order;--the predominant emotion of their minds overflowing spontaneously on all the objects which present themselves to their fancy, and calling out from them, and colouring with their own hues, those that are naturally emblematic of its character, and in accordance with its general expression. It would be easy to show how habitually this is done, by Shakspeare and Milton especially, and how much many of their finest passages are indebted, both for force and richness of effect, to this general and diffusive harmony of the external character of their scenes with the passions of their living agents--this harmonizing and appropriate glow with which they kindle the whole surrounding atmosphere, and bring all that strikes the sense into unison with all the touches the heart.