In the brief opening scene of Macbeth, the foreboding statement of the "three sisters"--"Fair is foul, and foul is fair"--establishes the dilemma that faces Macbeth of how to distinguish reality against appearances and the disharmony that is created in Nature and within the natures of Macbeth and Lady Macbeth. This disharmony that is created is mainly a result of the disturbance of the world order of the Elizabethan Age. In fact, the "Chain of Being" constitutes the plots of many of Shakespeare's plays, as well as establishing the mental states of the main characters. So, with the murder of King Duncan, the world's harmony collapses in Macbeth.
The beginning of the disharmony of Nature stems from the world of the witches, who consider evil deeds as "fair." Thus, the preternatural realm skewers the harmony in nature and as Macbeth begins to give credence to their predictions, he then finds fairness in the foul. For instance, in Scene 3 of Act I, although the weather is foul, Macbeth has been victorious in battle, so he feels the day is 'fair': "So foul and fair a day I have not seen" (1.3.38).
With no significance to good or bad in Nature, the natures of Macbeth and his wife, Lady Macbeth, gradually disintegrate. Valorous in his fight with Macdonaldwald, Macbeth becomes pusillanimous:
Whose horrid image doth unfix my hair
And make my seated heart knock at my ribs,
Against the use of nature? (1.3)
Then, in his monologue prior to his regicide, Macbeth reveals his dishonor as he admits that killing Duncan, his kinsman, is something he will do to satisfy his ambition:
...I have no spur
To prick the sides of my intent, but only
Vaulting ambition, which o'erleaps itself
And falls on th' other (1.7.)
Similarly, Lady Macbeth becomes cruel as she unsexes herself and chides Macbeth for his lack of courage:
My hands are of your color, but I shame
To wear a heart so white....
A little water clears us of this deed:
How easy is it then! (2.2)
And, yet she later becomes so delusional that she finds it impossible to wash out the "damned spot" of blood upon her guilty conscience and unnaturally tortured mind.
Another way in which the Disharmony in Nature theme is illustrated in Macbeth is through the use of the rhetorical device prolepsis. This device is used for the representation of an anticipated event as already having happened. This prolepsis can occur as a figure of speech, but it can also be a figure of thought as a person feels in his mind that the action is already a fait accompli. So, in Act V when Macbeth's messenger reports that he has seen Birnam Wood begin to move, prolepsis as a figure of thought takes place in the mind of Macbeth. With this unnatural sight, Macbeth becomes undone, losing all faith in life:
If this which he avouches does appear,
There is nor flying hence nor tarrying here.
I'gin to be aweary of the sun,
And wish th' estate o; th' world were now undone. (5.7)
By embracing the unnatural in the predictions of the witches with his murder of the king, who was thought of as having divine rights in the Chain of Being, Macbeth along with Lady Macbeth embrace the "foul" and upset the harmony in Nature.