What do you think " Fair is foul, foul is fair " mean in the Shakespeare play?

Question

Just an in depth answer, so i can understand Shakespeare's extraordinary work. :) 

Answer 1

Fair is foul, and foul is fair:
Hover through the fog and filthy air. (1.1.12-13)

i.e., Everything we delight in is evil to other beings and vice versa:
So let us hover through the fog and murky air.

 

Fair here is in the context of something like a "fair maiden", i.e. something appealing and nice, not something just or equal.