The line "fair is foul and foul is fair" is demonstrated in the entire play. Can you identify those instances?
When the Battle's Lost and Won
Macbeth is a play based on contradictions and equivocations. There is a contradiction on almost every page. I'm as sure as I can be that Shakespeare planned it that way. Indeed, the witches themselves rely on double meanings and contradictions all the time:
Lesser than Macbeth, and greater.
Not so happy, yet much happier.
Thou shalt get kings, though thou be none.
So all hail, Macbeth and Banquo!
Banquo and Macbeth, all hail!
Want more? Lady Macbeth asks to be unsexed and Macbeth later says to her:
Bring forth men-children only,
For thy undaunted mettle should compose
Nothing but males.
And she refers to him as a woman:
O, these flaws and starts,
Impostors to true fear, would well become
A woman's story at a winter's fire,
Authorized by her grandam.
More? The porter's speech before answering the knock the door is all contradictions:
Here's a farmer that hanged himself on th’ expectation of plenty...here's an equivocator that could swear in both the scales against either scale, who committed treason enough for God's sake yet could not equivocate to heaven...here's an English tailor come hither, for stealing out of a French hose...But this place is too cold for hell.
More? In Act 4, Scene 3, the entire first part of the conversation between Malcolm and Macduff is equivocation and contradiction. Malcolm is telling Macduff things about himself that are comletely opposite of the truth.
I could give you much more, but just know that the play, Macbeth, is based upon the idea that the world has been turned upside down: good is seen as evil, evil as good, men act like women, women act like men, truth is taken for lies and lies for truth, killing is good and then killing is bad, and so on and so on. "Fair is foul, and foul is fair," for sure and everywhere.
OK, here's one more in parting:
Angels are bright still, though the brightest fell.
Though all things foul would wear the brows of grace,
Yet grace must still look so.
Just open to any page and there they are, like bones that support the body.
Seeing that this is a theme of the play, it can be found in several moments. The very idea that Lady MacBeth would conspire with MacBeth to slay the king is representative of this line. The underlying premise of the line is that what is considered to be immoral or unjust has been created or conceived to be action to be taken. The moral order that used to uphold reality has been suspended and in its place, the inverse of this structure can become the new structure. Moments where what could be deemed as one thing, but actually represent another can be seen. The presence of the witches, themselves, might be such an example. On one hand, the three witches could be seen as something evil or unholy, definitely to be rejected. However, their presence being embraced by Macbeth would be another instance of "fair is foul" and the idea that things are not what they seem to be. Extending this would be Lady Macbeth's acknowledgement of wrong and her complicity. On one hand at the start of the play, she is the embodiment of the animating spirit behind immoral actions. Yet, through the course of the play, she becomes increasingly timid, being wrapped and subsumed the force of her own culpability. Her death at the end of the play, triggering Macbeth's final soliloquy reflects the idea of things might be different that what they seem to be.
There are verbal intratextual resonances of this subversive chiasmic expression in the whole play. A few instances are
1. When Macbeth in Act I Scene 3 refers to the fair and foul day on his entrance for the first time. It shows his psychic proximity with the evil (the witches, he is yet to meet)
2. When in the second scene of the first act, the bleeding captain says that both sunlight and storms come from the same Eastern horizon
Macbeth, the play shows Macbeth's journey from fair to foul. Inverting the simplistic moral pattern of a morality play, Shakespeare connotes the uncanny mutuality of the good and the evil. What he suggests is the non-essentializable quality of the ethical questions--a beyond to the good and evil. The entire play is founded on this problematic notion of the evil, the appearance-reality dichotomy and the way the fair slips into the foul in ways both subjective and objective. It is a cosmic irony that the fairest of minds fall prey to evil temptations.