A Deed Without A Name: The Significance Of Witches In Macbeth Shakespeare uses the witches in Macbeth for two main reasons. Firstly, to show how desire, ambition and greed are often more powerful than reason, and secondly for dramatic effect which comes from the confusion surrounding their identity and the vagueness of their prophecies. These two reasons, and the characters they represent, can be seen as two of the main, but somewhat hidden, factors behind Macbeth. The witches are fundamental characters because they are able to prophesize the future. In many situations, characters are faced with the decision of whether or not to rely