Like Adam and Hetty, Arthur is a very complex character, an amalgam of good and bad qualities. He is basically a pleasant and kindhearted young man who hates the thought of hurting anyone and who likes to be on good terms with all who know him. He is a rich man and an aristocrat who intends to use his wealth and social position for good ends; unlike Hetty, his dreams of the future do not concern themselves with his own happiness alone; he wishes to benefit others too. Arthur is a blithe spirit, happy, charming, and friendly.
But he is very unrealistic. Because of his background, he does not feel that he has to work to get what he wants; he thinks that his dreams will come true without effort. He also does not know himself very well. Arthur is very self-confident, but without reason; he does not possess the self-discipline which could justify his confidence. He is aware of his own faults — his tendency to vacillate, for example — but he cannot bring himself to correct them. His excellent opinion of his own virtue prevents him from thinking in terms of self-improvement, and he is too weak to follow his own conscience without being forced to do so.
This set of attitudes gets Arthur into trouble and prevents him from getting himself out. He knows that his desire for Hetty is impractical, but that does not stop him from seducing her; he wants her and he is used to getting what he wants, though he is not ruthless. Later he refuses to believe that anything bad will come of the relationship, and he continues to play the role of the honorable man even while behaving dishonorably; his objective actions do not influence his self-image. Finally, he cannot bring himself to break off the relationship because he is so kind-hearted; he can't bear to give Hetty pain.
Arthur is thus an emotional and moral drifter; he does not guide himself by any fixed and realistic principles, and his good and bad qualities conspire to lead him to ruin another person's life. He is not completely unconcerned about other people, but his basic attitude is egotistical; he cares more about his own desires than he does Hetty's, for example, and his primary motivation for wanting to help his tenants seems to be to win their respect and praise. This selfishness, combined with his delusions about his virtue, make him irresponsible; he does things without calculating their effects on himself or the other people involved.
Experience sobers Arthur. When Adam confronted him with his guilt in the grove, he was able to rationalize his actions and maintain his self-image. But when Hetty abandons his child to its death, he realizes that if one is to accomplish one's goals, he must act so as to bring them about. He sees the potential for evil that he possesses, breaks free from the unrealistic self-image he had previously held, and tries to improve the situation he has created as much as possible. After performing a symbolic penance, he returns home, ready to work for good ends without egotism or pretense. Like Adam and Hetty, he has accepted responsibility and become humble.