Answer :
Your Dictionary defines "cosmic irony" as "Cosmic irony can be attributed to some sort of misfortune. This form of irony is the result of fate or chance and the outcomes are not a result of the characters' actions. So it can seem as if an outside force has a hand in the situation.
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In the given stanza from "The Chimney Sweepers," cosmic irony has been used to imply that in order for the sweepers’ conditions to improve, they have to die.
In Tom's dream the Angel tells him that he should continue to do his duty of chimney sweeping despite the physical, mental and emotional trauma he undergoes on a daily basis. This is because his situation is not likely to get better. The condition of chimney sweepers can only improve in the afterlife after their death. She does not do anything to improve his present condition.
