Miss Lockwood, in the Introduction to her admirable collection of English sonnets, [Footnote: Sonnets, English and American, selected by Laura E. Lockwood. Houghton Mifflin Company, 1916.] makes a still briefer summary of the thought-scheme of the regular Italian sonnet: it "should have a clear and unified theme, stated in the first quatrain, developed or proved in the second, confirmed or regarded from a new point of view in the first tercet, and concluded in the second tercet. It had thus four parts, divided unevenly into two separate systems, eight lines being devoted to placing the thought before the mind, and six to deducing the conclusion from that thought."
A surprisingly large number of sonnets are built upon simple formulas like "As"—for the octave—and "So"—for the sestet—(see Andrew Lang's "The Odyssey," Oxford, No. 841); or "When" and "Then" (see Keats's "When I have fears that I may cease to be," Oxford, No. 635). A situation plus a thought gives a mood; or a mood plus an event gives a mental resolve, etc. The possible combinations are infinite, but the law of logical relation between octave and sestet, premise and conclusion, is immutable.
Let the reader now test these laws of sonnet form and thought by reading aloud one of the most familiarly known of all English sonnets—Keats's "On First Looking into Chapman's Homer":
"Much have I travell'd in the realms of gold,
And many goodly states and kingdoms seen;
Round many western islands have I been
Which bards in fealty to Apollo hold.
Oft of one wide expanse had I been told
That deep-brow'd Homer ruled as his demesne;
Yet did I never breathe its pure serene
Till I heard Chapman speak out loud and bold:
Then felt I like some watcher of the skies
When a new planet swims into his ken;
Or like stout Cortez when with eagle eyes
He stared at the Pacific—and all his men
Look'd at each other with a wild surmise—
Silent, upon a peak in Darien."
Read next another strictly Petrarchan sonnet, where the thought divisions of quatrains and tercets are marked with exceptional clearness, Eugene Lee-Hamilton's disillusioned "Sea-Shell Murmurs":
"The hollow sea-shell that for years hath stood
On dusty shelves, when held against the ear
Proclaims its stormy parent; and we hear
The faint far murmur of the breaking flood.
"We hear the sea. The sea? It is the blood
In our own veins, impetuous and near,
And pulses keeping pace with hope and fear
And with our feelings' every shifting mood.
"Lo, in my heart I hear, as in a shell,
The murmur of a world beyond the grave,
Distinct, distinct, though faint and far it be.
"Thou fool; this echo is a cheat as well,—
The hum of earthly instincts; and we crave
A world unreal as the shell-heard sea."
And now read aloud one of the best-known of Shakspere's sonnets, where he follows his favorite device of a threefold statement of his central thought, using a different image in each quatrain, and closing with a personal application of the idea: