the character in one thousand dollars
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To me, there is only one real character in this story -- it is the young man, Robert Gillian, who gets the $1000 and must decide what to do with it. As the story progresses, we find out a great deal about his character.
Young Gillian clearly has been something of a playboy and a prodigal. He seems to have gone around wasting money on frivolous things. For much of the story, this seems to be his true character. However, at the end of the story, we come to find out that he has a serious side. More importantly, we find that one of the most important aspects of his character is that he is unselfish and he knows how to act out of love. His final action in the story shows this -- he knowingly sacrifices a fortune so the woman he loves can have it instead.