Along with the descriptions of the twenty-eight incarnations that make up the largest section of “Book I: What the Caliph Partly Learned”and the poems “The Phases of the Moon” and “All Souls’ Night,” which frame the main text, “Dove or Swan” is one of the few sections of A Vision that did not undergo a radical revision when Yeats rewrote his philosophical treatise. Indeed, Yeats goes out of his way in “A Packet for Ezra Pound” to call attention to these unchanged sections:
The first version of this book, A Vision, except the section on the twenty-eight phases, and that called “Dove or Swan” which I repeat without change, fills me with shame. I had misinterpreted the geometry, and in my ignorance of philosophy failed to understand distinctions upon which the coherence of the whole depended, and as my wife was unwilling thather share should be known, and I to seem sole author, I had invented an unnatural story of an Arabian traveller which I must amend and find a place for some day because I was fool enough to write half a dozen poems that are unintelligible without it. (AVB19)
If we, for the moment, take this admission at face value, Yeats is essentially stating these two core texts form the foundation of A Vision(1937). They are the framework of Yeats's system— “the hard symbolic bones under the skin” (AVB24)—upon which he structures his interpretations and understanding of the interchange between the primary and the antithetical.
This foundation, however, is more than metaphor. Because they are constantly grounded in particulars and provide illustrative examples, the description of the twenty-eight incarnations and “Dove or Swan” are the most concrete, comprehensible sections in both editions. As such, they serve a particular function within A Vision B: they are the specific expressions of Yeats's system which follow after and balance against the sections that deal in the abstractions of the more theoretical and philosophical concepts—a structural balance appropriate to his duality-based system.