1. The Witches' Prophecy: After consulting the witches in Act 1, Macbeth learns of the prophecies that he will become king and that Banquo's descendants will eventually rule Scotland. This prophecy plants seeds of envy and ambition in Macbeth's mind. He sees Banquo as a potential rival and threat to his newly acquired throne, fearing that Banquo's future progeny might displace him or his lineage.
2. Banquo's Keen Perception: Macbeth is aware that Banquo is wise and perceptive, which makes him a potential threat to Macbeth's deceitful and murderous schemes. Banquo suspects foul play in Duncan's death and is hesitant to trust Macbeth. His doubt and curiosity raise concerns in Macbeth's mind, increasing his fear that Banquo might uncover the truth and expose him.
3. The Ghost of Banquo: After Macbeth has Banquo assassinated, the guilt and paranoia that consume him manifest in the form of Banquo's ghost haunting him. The ghost serves as a constant reminder of Macbeth's crime and further intensifies his fear and insecurity. Banquo's presence, even as a ghost, continues to unsettle Macbeth, making him feel threatened by the very person who he thought he had successfully eliminated.
4. Loss of Control: Macbeth's fear of Banquo also reflects his diminishing control over his own life and ambition. The pursuit of power has led him down a path of violence and deception, but he realizes that Banquo's existence poses a challenge to his ability to maintain his grip on the throne. Banquo's integrity and moral compass add to Macbeth's sense of vulnerability and uncertainty.
5. Paranoia and Guilt: As Macbeth's guilt and paranoia deepen, his perception of Banquo as a threat becomes more irrational. He starts to see Banquo's presence and influence everywhere, even when there is no tangible evidence of his involvement. This paranoia further fuels Macbeth's fear and causes him to take desperate measures to protect his position.
In conclusion, Macbeth's fear of Banquo stems from a combination of factors, including the witches' prophecies, Banquo's innate wisdom and suspicion, the haunting presence of Banquo's ghost, and Macbeth's own increasing paranoia and guilt. Banquo's existence challenges Macbeth's sense of control and security, posing a profound threat to his ambitions and peace of mind.