Final answer:
The witches in 'Macbeth' symbolize evil and contribute to themes of moral ambiguity, playing a central role that underscores the supernatural and its influence on human actions.
Step-by-step explanation:
The witches in Shakespeare's play 'Macbeth' serve as a potent source of evil and contribute to the overarching theme of moral ambiguity and deception. Through their prophecies, the witches instigate Macbeth's descent into tyranny and chaos, accentuating the struggle between the natural and unnatural in the play. They are not symbols of goodness or purity nor do they guide Macbeth towards a positive outcome; instead, their significant role underscores the presence of supernatural elements and the resulting human folly and ambition.