Fate plays a large role in Shakespeare's Macbeth. Not only do the weird sisters use it to wreak havoc among the Scottish nobility, but many people throughout the play try to tempt fate. Macbeth does it, as does Lady Macbeth. Then, later in the play, even Malcolm, Macduff and the other revolutionaries try to alter fate. Throughout the play of Macbeth, Shakespeare chooses to use animals to portray foreshadowing, to develop character and to get a wide variety of emotions from the audience.
To the weird sisters, fate is not something to be overly concerned with. However, their superior, Hecate, obviously thinks that it was important enough to discipline the weird sisters verbally for abusing it. To the weird sisters, fate, and for that matter it seems, time, is merely as water and bread are to Macbeth: they exist and can be altered. This view of fate is not as ambivalent as the other view, but is more a view along the lines of Thomas Aquinas or Kurt Vonnegut. According to Aquinas, time is something that you both exist in and are affected by or you not. One is either subject to the limitations of time or one is not. For instance, God is outside the normal limitations of time and is therefore immortal. In Macbeth, it seems, the witches are a transient hybrid of those in time and those not in time. That is to say, they can travel in and out of time at will. This ability allows them to both see the future and to change its very course. This of course proves to be an illogical paradox when examined analytically, but Shakespeare's great work is brimming with paradoxes ("Fair is foul, and foul is fair" I.i.11). .
This ability leads to some interesting and important moments in the play. For one, the witches seem to already know the consummation of both Macbeth and Banquo's respective fates. However, they, for some reason unbeknownst to the audience, deem it necessary to interfere with this fate and tell Macbeth and Banquo about their futures.