It has long been a commonplace of criticism that great poets seldom invent their myths; and it may in time become a commonplace of criticism that they seldom invent their forms.  But in default of the lesser invention, they have the larger imagination; and there is no pedantry in seeking to emphasize the distinction between these two qualities, often carelessly confused.  Invention is external and imagination is internal.  The poets, by the mere fact that they are poets, possess the power of imagination, which alone gives vitality and significance to the ready-made plots they are willing to run into ready-made molds.  Invention can do no more than devise; imagination can interpret.  The details of ‘Romeo and Juliet’ may be more or less contained in the tale of the Italian novelist; but the inner meaning of that ideal tragedy of youthful love is seized and set forth only by the English dramatist.

Imagination in its fullest meaning must be held to include invention; but invention is only one of the less important elements of imagination; and it is the element which seems to be more or less negligible when the other elements are amply developed.  La Fontaine, one of the most individual of French poets, devised only a few—­and not the best—­of the delightful fables he related with unfailing felicity.  Calderon, who was the most imaginative of the dramatists of Spain, was perhaps the least inventive of them all, contentedly availing himself of the situations, and even of the complete plots of his more fertile fellow-playwrights; and two of his most characteristic dramas, for example, two in which he has most adequately exprest himself, the ‘Alcalde of Zalamea’ and the ‘Physician of His Own Honor,’ are borrowed almost bodily from his fecund contemporary Lope de Vega.  Racine seems to have found a special pleasure in treating anew the themes Euripides had already dealt with almost a score of centuries earlier.  Tennyson, to take another example, displayed not a little of this “sluggish avoidance of needless invention,” often preferring to apply his imagination to the transfiguring of what Malory or Miss Mitford, Froude or Freeman had made ready for his hand.  This eschewing of overt originality fitted him all the more to be spokesman of his time, and to voice the ideals of his race and of his day.  Tennyson, so Sir Leslie Stephen told us, “could express what occurred to everybody in language that could be approached by nobody.”  Browning, on the other hand, made his own plots, and on the whole made them none too well, especially in his dramatic poems, in the structure of which he was entirely neglectful of the accepted forms of the theater of his own time—­accepted forms of which Shakspere and Moliere would have availed themselves instinctively.  It was not Browning, but Whitman—­and Whitman in 1855, when the bard of Manhattan had not yet shown the stuff that was in him—­that Lowell had in mind in the letter where he says “when a man aims at originality he acknowledges himself consciously unoriginal....  The great fellows have always let the stream of their activity flow quietly.”