Every poet, then, is a versifier; every fine poet an excellent one; and he is the best whose verse exhibits the greatest amount of strength, sweetness, straightforwardness, unsuperfluousness, variety, and oneness;—oneness, that is to say, consistency in the general impression, metrical and moral; and variety, or every pertinent diversity of tone and rhythm, in the process.... It is thus that versification itself becomes part of the sentiment of a poem, and vindicates the pains that have been taken to show its importance. I know of no very fine versification unaccompanied with fine poetry; no poetry of a mean order accompanied with verse of the highest.

(Leigh Hunt: What is Poetry? Cook ed., pp. 37-40, 61.)

No literary expression can, properly speaking, be called poetry that is not in a certain deep sense emotional, whatever may be its subject-matter, concrete in its method and its diction, rhythmical in movement, and artistic in form.... That poetry must be metrical or even rhythmical in movement, however, is what some have denied. Here we touch at once the very root of the subject.... While prose requires intellectual life and emotional life, poetry seems to require not only intellectual life and emotional life but rhythmic life.... Unless the rhythm of any metrical passage is so vigorous, so natural, and so free that it seems as though it could live, if need were, by its rhythm alone, has that passage any right to exist? and should it not, if the substance is good, be forthwith demetricized and turned into prose? ... Aristotle ignored, and Plato slighted, the importance of versification (though Plato on one occasion admitted that he who did not know rhythm could be called neither musician nor poet).... On the whole, however, the theory that versification is not an indispensable requisite of a poem seems to have become nearly obsolete in our time. Perhaps, indeed, many critics would now go so far in the contrary direction as to say with Hegel (Æsthetik, iii. p. 289) that "metre is the first and only condition absolutely demanded by poetry, yea even more necessary than a figurative picturesque diction."

(Theodore Watts: Article on "Poetry" in Encyclopædia Britannica.)

Verse-rhythm in words is the imposition of a sensible order on what naturally and normally has only a logical order; and there is piquancy in the feeling that so little is this ideal control a fettering instrument, that each order seems to gain verve and spontaneity from the other, or rather from the latent sense that the other, though present and operative, is powerless to hamper it. Much more important, however, is it to notice how the sense that one single thing—the word-series—is lending itself to this joint dominance may take the form of a sort of transfigured surprise. (The root-principle here involved is the old one of "unity in variety," the single line of words, "dominated at once by the idea which they express in their grammatical connection and by their metrical adjustment," clearly possessing two independent functions or aspects. See the fuller discussion of "The Sound-element in Verse," in chapter xix. of The Power of Sound.) ... When, as in verse, the sounds are pointedly addressed both to the ear and to the understanding, the rarity of the combination of aspects contributes a strain of feeling partly akin to that with which we follow an exhibition of skill, and partly to that with which we receive an unexpected gratuity....

Nor is this all. Rhythm perpetually not only transfigures the poetical expression of an idea, but makes the existence of that expression possible. This is tolerably obvious in the case of what is often called par excellence poetical language—language which keeps clear of prosaic homeliness and prosaic precision and of technical and abstract terms, and confines itself to a more picturesque and loftier vocabulary.... Clearly it is the rarity of rhythmic, as compared with non-rhythmic, speech that supports such rarity of poetic as compared with non-poetic diction; that is to say, verse, being in one respect—namely, its effect on the ear—a marked exception from ordinary language, thereby establishes for itself the means of being exceptional, without seeming unnatural, in other ways....

... In dwelling on the non-reasonable part in poetical beauty, I am in no way committed to the assertion that all its constituents are excluded from prose, but only to the assertion that the metrical form makes a difference of kind. It cannot be for nothing that the very idea of "poetical prose" inspires dread; and the instances of prose-writing where we find delight of the intangible and non-reasonable kind are exceptions that only prove the rule. One has but to test by self-examination the living force of words in a specimen of verse and of poetical prose which may respectively seem to oneself first-rate of their kind. For such typical passages may often be regarded as fairly on a par in respect of the ideas and emotions which they reasonably express; and the prose may unquestionably further resemble the poetry in a certain subtle individuality of life in its more prominent words, so far as this life can be quickened in them by the idea itself, aided by such qualities of sound-arrangement as are possible apart from metre. So far the poetical merits of the respective passages may be equal; yet only one of them is Poetry.... Language, which in prose does little more than transmit thought, like clear glass, becomes—even as that becomes—by art's adjustments and the moulding of measured form, a lens, where the thought takes fire as it passes. The poet speaks through a medium which seems to intensify the point and to extend the range of what he would tell us by some power outside his own volition. Such a power, in fact, a rhythmic order, in its fundamental appeal to human nerves, literally is.... The ictus of the verse comes upon us as the operative force which shocks the words into their unwonted life.

... In considering the total contribution of metre to imaginative language, it is impossible to overlook the quality of permanence. I do not mean permanence merely in the sense that metrical words live in the memory.... This is, of course, a most important fact; but I am here dealing only with elements of effect that enter into the actual moment of enjoyment.... It is a sense of combined parts, and their indispensableness one to another, which gives us a sense of permanence in an arch as compared with a casual heap of stones; it is a similar indispensableness which gives to metrical language an air of permanence impossible even to the most harmonious sentence whose sounds conform to no genuine scheme. And again, in the case of this constituent as of the others, we have no difficulty in seeing that its influence is really a joint one of sound and sense—that, though founded in the nature of metrical sound as such, it is not merely a sound-quality superposed ab extra on the intelligible beauty of the words, but depends for its existence on their intelligible character.... We cannot glory in the enshrining for memory of things that we do not care to remember. But for that which is of true spiritual significance the fairly-fitted body of sound is greeted as the inevitable investiture; and thus justified and quickened, the strength of the mutually indispensable parts seems no longer that of mere structure but of organic life.

(Edmund Gurney: Essay on "Poets, Critics, and Class-Lists," in Tertium Quid, vol. ii. pp. 162-179, passim.)

Why have poets always written in metre? The answer is, Because the laws of artistic expression oblige them to do so. When the poet has been inspired from without in the way in which we saw Scott was inspired to conceive the Lay of the Last Minstrel—that is to say, when he has found his subject-matter in an idea, universally striking to the imagination, when he has received this into his own imagination, and has given it a new and beautiful form of life there, then he will seek to express his conception through a vehicle of language harmonizing with his own feelings and the nature of the subject, and this kind of language is called verse. For example, when Marlowe wishes to represent the emotions of Faustus, after he has called up the phantom of Helen of Troy, it is plain that some very rapturous form of expression is needed to convey an adequate idea of such famous beauty. Marlowe rises to the occasion in those "mighty lines" of his: