The poem in which he has most clearly formulated the general principles underlying the growth of art is the "Parleying" with Charles Avison. Though music is the special art under consideration, the rules of growth obtaining in that are equally applicable to other arts. They are found to be, as we should expect in Browning, a combination of the ideas of evolution and conservation. Though the standards of art change and develop, because as man's soul evolves, more complex forms are needed to express his deeper experiences, his wider vision, yet in each stage of the development there is an element of permanent beauty which by the aid of the historical sense man may continue to enjoy. That element of permanence exists when genuine feeling and aspiration find expression in forms of art. The element of change grows out of the fact that both the thought expressed and the form in which it is expressed are partial manifestations of the beauty or truth toward which feeling aspires; hence the need of fresh attempts to reach the infinite. The permanence of feeling, expressing itself in ever new forms, is brought out finely in this passage: "Truths escape Time's insufficient garniture: they fade, They fall--those sheathings now grown sere, whose aid Was infinite to truth they wrapped, saved fine And free through march frost: May dews crystalline Nourish truth merely,--does June boast the fruit As--not new vesture merely but, to boot, Novel creation? Soon shall fade and fall Myth after myth--the husk-like lies I call New truth's Corolla-safeguard." In another passage is shown how the permanence of feeling conserves even the form, if we will bring ourselves into touch with it: "Never dream That what once lived shall ever die! They seem Dead--do they? lapsed things lost in limbo? Bring Our life to kindle theirs, and straight each king Starts, you shall see, stands up."