Thank you for sharing such a thoughtful reflection! About the word “claim,” swapping it for “the hopeless” doesn’t quite work here. “Claim” means presumption is not just weakness or suffering but that it also has a kind of right or demand, which is important in the poetic sense here. “The hopeless” usually refers to people without hope, so it doesn’t fit as something presumption can have. If you do want to focus on weakness, “helplessness” might work better but it loses the balance that the word “claim” brings. As for your point about “becoming heroism,” I agree that being singular today is tough with how fast and fractured everything is. It probably doesn’t look like Dickinson’s quiet reclusive heroism anymore, but standing out in your own way is still a kind of heroism. Hope this helps clarify your questions!

These quotes come from private letters that Emily wrote to her sister-in-law, Susan. If the words seem obscure, it is because they were only intended to be understood by Susan. Emily never dreamed that one day millions of people would want to analyze every word "Emily Dickinson" ever wrote. Given that, it is impossible to be sure about exact meanings. Susan was a brilliant imaginative person, so Susan's "Arabian Nights" might refer to stories Susan has told Emily, or spellbinding conversations with her. It is complimentary because there can be nothing drab about "Arabian Nights". The heart's "arithmetic", by contrast, is drab. I do not know what were the drab burdens to which Susan's heart was subjected, but in any case the contrast between the drab and the fantastical has unsettled Susan since Emily feels sorrow for her "day". It appears that Susan felt pulled in many directions: towards the fantastical and towards the drab. Emily feels that Susan's courage to withstand forces pulling her in both directions and remain one "singular" ("single", really) person is heroic. The line "To lose ... as claim" is an exemplar of Emily's odd but brilliant thinking. Who but her could have uttered such words? Their meaning is clear though. She is saying that claiming to lose something you don't own is kind of crazy ("eccentric"). If this (imagined) loss is painful, it makes sense for Emily to call it a "bereavement" because she is, after all, a poet, and loves to exaggerate. Nonetheless, it is a false claim. It is not a bereavement. You cannot lose something you don't have. But so what? She is a poet! She is brilliant! She will Presume these things to be so. She has a right to do that because she inhabits a world of imagination.