Rephrase the thesis in a new way
The answer to this question is:
Radiation
The chorus in an Ancient Greek play was extremely important because it helped the viewers to follow along. Often times it summarized what happened in a certain act/scene/play, which helped people who did not understand it to, well, understand it. It also often provided insight into characters minds. It told things about the characters that they could not tell about themselves, which could help the viewer predict what was going to happen in the upcoming scenes.
Answer:
The line 'So Eden sank to grief' is an allusion, or literary reference, to the Biblical story about The Garden of Eden, a perfect paradise until Eve ate from the Tree of Knowledge. By making this reference, Frost is implying that the idea nothing good can last is an old one; it's part of our human experience.
