The Influence of External Forces There were many external forces that influenced Macbeth 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 Macbeth. The apparitions influenced Macbeth 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 matter how hard Macbeth tried, he could not avoid the influence of what others had to say. The first external force that influenced Macb