I think Macbeth is so quick to take the witches' predictions seriously because he is a very ambitious man. The first witch hails him as Thane of Glamis, which he is. Then the other witch hails him as Thane of Cawdor, which he is not, and the third witch tells him that he is going to be king. After Ross and Angus tell him he was rewarded by King Duncan as Thane of Cawdor, he starts thinking that what the witches said can become true. He can become King of Scotland. <em>"It’s just like they said—now I’m the thane of Glamis and the thane of Cawdor. And the best part of what they predicted is still to come." </em>