(1) There is the twofold division of the Book, while the other Books of Fableland have distinctly a threefold division. Herewith is coupled the duplication of its content; the second part repeats what is contained in the first part; or the first part tells in advance what is to be done in the second part. Thus the structure images dualism: Thought and Action, Word and Deed, Idea and Reality, Prophecy and Fulfillment. Yet it also hints the oneness in the dualism. (2) The next point in structure is the threefold subdivision of each of the two parts. That is, now the structural principle falls back into that of the preceding Books of Fableland. Each part has its three main adventures with their respective environments and shapes, quite as each Book hitherto has had. What does this suggest to the reader--this duplication of the threefold form of the Book? (3) Finally comes the very peculiar structure of the second adventure, which we have above called the Double Alternative. The dualism of the Book we may say, is now doubled, and transformed into the middle one of the three grand trials or exploits which the Hero has to pass through. The monster Scylla is here to be noted, with its six necks and heads, three on each side of the body, wherein again the triple is duplicated, though the body is certainly one. It was this monster which did most harm to Ulysses, snapping up six of his companions in the passage. Such are the main points in the structure of the present Book, assuredly as great a marvel as anything recorded in the same, when it is once fully beheld. That it is intimately connected with the thought of the Book, is indeed the very form and mould thereof, is felt by every careful reader. But what is this thought? Here the difference begins, and the conflict of opinion ranges over and into fields diverse and far apart. II. It may be said that the interpretations suggested by these three adventures--with the Sirens, with Scylla and Charybdis, and with the Oxen of the Sun--belong to two extremes; those of Nature and of Mind. Readers and commentators of different character and training will differ; one set will lean to the physical view, the other to the spiritual. It is our opinion that both views can find justification in the poem. We may first look at the physical interpretation.