Stirling, Brents. "'Look, how our partner's rapt'."
Unity in Shakespearian Tragedy: The Interplay of Theme and Character. New York: Columbia UP, 1956. 139-156.

Opening his chapter on Macbeth, Stirling asserts, "The exceptional unity of Macbeth is partly based upon four themes--darkness, sleep, raptness, and contradiction--which combine to give the play much of its character" (139). A little later, Stirling adds:

Such an unity of design would lack importance if it did not contribute to an interpretation of the play, and for the sake of clarity I shall suggest the interpretation here. Macbeth is based upon the familiar tragic motive of sin and self-destruction which are compulsive. The surrender to the witches is a surrender to "instruments of darkness," to "secret, black, and midnight hags," and with it appears Macbeth's raptness, an obsessive state which implies contradiction, since from its onset "nothing is but what is not." Contradiction within raptness now governs both character and play, as a great rhetoric of conscience accompanies the almost hypnotic murder of sleep. And as obsession under the spell of darkness leads to added murder--violence dedicated to peace and sleep--the ultimate contradiction occurs. Macbeth's abstraction gives way to awareness of reality, while Lady Macbeth's early command of pseudo-reality advances into the guilty raptness of walking sleep.   (140-141)
Stirling then proceeds through the play, discussing examples of images of darkness, sleep, raptness, and contradiction.

The problem is, the analysis of character doesn't keep pace with the examination of the themes which interest Stirling. Too often, he merely points out occurrences of images, without commenting on "the interplay of theme and character."

Bottom Line: Promising premise, mediocre execution.