The sentiment expressed by the tramp in the letter:
The tramp in the letter expresses a mixture of desperation, gratitude, and hope. He begins the letter by acknowledging his dire circumstances and confessing that he is on the run, seeking refuge. The tramp describes himself as a "wretched and starving being" who is in desperate need of help. He expresses his gratitude to Edla for her kindness and compassion, stating that she is the only one who has shown him any sympathy.

The tramp also conveys a sense of hopelessness and despair, emphasizing that he is a "lost man" who has no one to turn to. He explains that he has been treated harshly by the world and has resorted to stealing and begging for survival. Despite his difficult circumstances, he expresses a glimmer of hope in the form of a request for forgiveness and redemption. The tramp believes that Edla's kindness could potentially save him from his downward spiral and give him a chance at a better life.

Why had he signed himself as Captain von Stahle?
The tramp signs himself as Captain von Stahle to create an impression of dignity and authority. By adopting this false identity, he aims to evoke sympathy and manipulate Edla into helping him. The title of "Captain" suggests that he once held a position of importance and respect, which he hopes will make Edla more inclined to assist him.

Signing as Captain von Stahle also serves a strategic purpose. The tramp understands that people tend to be more compassionate towards those who have fallen from a higher social status. By presenting himself as a fallen nobleman, he believes he can elicit more sympathy and support from Edla.

Additionally, the tramp's choice of the name "von Stahle" may be significant. "Stahle" sounds similar to the word "stale," which could symbolize the tramp's current state of life - worn-out, hopeless, and in need of rejuvenation. The juxtaposition of the noble title "Captain" with the potentially deteriorating surname "Stahle" may serve as a metaphor for his desperate desire for redemption and transformation.

Overall, the tramp's decision to sign himself as Captain von Stahle reflects his attempt to create an image of dignity and appeal to Edla's empathy and compassion.