Seldon

It seems to me that Selden's character in The House of Mirth is created to help the reader understand and realize some of the absurdities of the social scene. He is sort of on the fringe of this level of society and sort questions it himself with his relationship with Lily. He questions her actions and her values. Maybe Wharton is using him a "control" to sort of compare to with the rest of the characters and how they act in their world.