<Tr> <Th> Author </Th> <Td> Thomas De Quincey </Td> </Tr> <Tr> <Th> Country </Th> <Td> England </Td> </Tr> <Tr> <Th> Language </Th> <Td> English </Td> </Tr> <Tr> <Th> Genre </Th> <Td> essay, literary criticism </Td> </Tr>

What is the purpose of the knocking at the gate scene in macbeth