“ All his earlier work was naturalistic and realistic - Finally, in the last paintings, the canvasses became nonsense”
-Oliver Sacks 558
When the play first start 's Macbeth is referred to by King Duncan his “Worthiest cousin” but later on in the play Macbeth begins to show signs of mental illness perhaps due to traumatizing events such as killing Duncan, and ordering the murderers to hunt down Banquo, and his son. When Macbeth begins to see the ghosts of Banquo it shows signs of remorse or regret on his conscience, and basically it begins to ruin him. Just like Dr.P 's paintings at first they were sensible pieces of art and as the illness progressed so did his mentality.
“All hail, Macbeth, that shalt be king hereafter! -
Thou shalt get things, though thou be none”
-I iii 53-70
“He listed buildings on his right side, but none of those on his left – bisecting his visual memory and imagination”
-Oliver Sacks 556
When the witches tell Banquo that his children will be kings, Macbeth was also present. In which case Macbeth should have realized that Banquo 's sons would be a threat to him. But Macbeth was unable to see the larger image and only focused on what would happen to king Duncan, he did not expand his imagination but simply kept to the right side. Ofcourse later on Macbeth begins to see this, but it is too late and people have already begun suspecting him of killing King Duncan. If we look at the situation from another angle we might also find a paradox, would Macbeth have become king if the witches had not told him about his future in which case, Lady Macbeth would have never received the letter and couldn 't have persuaded Macbeth into murdering King Duncan. This also links back to belief and religion where if you believe something you would most likely strive for it and succeed.
“Glamis, and thane of Cawdor!
- When those that gave the thane of Cawdor to me
Promised no less