The Influence of External Forces There were many external forces that influenced on making his major decision. The decision was whether or no to kill King Duncan. These forces were the apparitions, the old witches, and Lady . The apparitions influenced by making him think he was invincible. The witches influenced Macbeth by telling him that he was going to become king. Lady Macbeth also influenced him by emasculating him. Although these factors influenced Macbeth, it was still his choice to act upon this decision. Still, no ....