In Act 1, Scene 3 of Macbeth, what does Macbeth's aside reveal about his thinking?
how does Banquo's comment support the "Fair is foul, foul is fair" theme?
In Act I, scene 3, Banquo and Macbeth encounter the three witches who in Act I have stated,
Fair is foul, and foul is fair,/Hover through the fog and filthy air (I, i, ll.10-11)
Upon the request of Macbeth to speak, the witches pronounce their predictions: Macbeth will be Thane of Cawdor and later King. To Banquo they say that he will beget kings without ever being one, but he will be "Lesser than Macbeth, and greater." Puzzled by these words Macbeth and Banquo, speaking in asides, wonder about the predictions made about them. When Macbeth says in an aside
Blamis, and Thane of Cawdor:/The greatest is behind
he entertains the idea that he will become king, an idea that seems "fair," or good. He then asks Banquo if he does not hope that the witches's prediction that his children will become kings will come true. To this Banquo remarks upon Macbeth's eagerness for power:
That [news], trusted home,/Might yet enkindle you unto the crown
Banquo warns Macbeth that what appears "fair" could be "foul," knowing the evil nature of the witches; in other words, the outcomes of Macbeth's actions could be disastrous if he is "won to the harm" of these predictions. Of course, the irony is that Macbeth does not heed Banquo's warning, and, while the predictions do come true, they are effected by extremely evil and "foul" methods.
Macbeth's asides reveal that his thinking serves his desire. Macbeth starts with his desire as a foregone conclusion--that he will be king, that the "Two truths" are indeed "happy prologues to the swelling act / Of the imperial theme." Macbeth sees himself king as sure as he sees himself Glamis and Cawdor. His back and forth considerations then, do not ponder the morality--the "ill" or the "good" of the prophecy--they justify his conclusion. In fact, in justifying, he plays the same trick--starts with the conclusion: "they cannot be ill, cannot be good" and supports his end with logical fallacy, with questions, not reason. And his answer: "I am Thane of Cawdor" restates the truth but proves nothing--the list states three truths: one past, one present, and one future; none causes another.
Also, Mac's thinking violates the identity principle: "nothing is / But what is not," for x = not x is impossible. Even "So foul and fair a day I have not seen," marks his thinking--he has not seen "fair and foul" because he thinks only in absolutes. He even sees chance in terms of "will"--the "may" relates to method not truth-- as does "Come what come may . . . ."
Banquo and the foul/fair idea: Banquo warns Mac about things not being what they seem and distinguishes the apparent from the real as he answers Mac's question. His questions seek rather than confirm truth, and he worries about contradictions, about morality: "What, can the devil speak true?"