Fagin, the mastermind among the criminals, is as ugly in appearance as he is repulsive in disposition, but he is not a one-dimensional figure. In Fagin, Dickens has attempted to portray a character who displays some of the complexities of normal human nature. When incensed, the old man may give way to savage rage, but on ordinary occasions he indulges in a mocking, sometimes sarcastic humor that earns him the nickname of "the merry old gentleman." This very fact is in itself an example of sardonic humor, of which Dickens is a master.
It is plain that Fagin's status among the thieves is a result of his considerable talents. He is shrewder and more reflective than his companions. While they may swagger with the cockiness of young men or brood like the sadistic Sikes, Fagin understands and appreciates the delicacy of their position and the urgent necessity for prudence and tireless vigilance when leading a life of crime. He demonstrates his analytical bent in his lectures to Oliver and Claypole on the theme of interdependence among the lawless.
When not caught off guard, Fagin can exercise extraordinary self-control, even under extreme stress. So, after recovering from the initial shock brought about by his discovery of Nancy's meetings with the enemy, he is able skillfully to prod Sikes to commit murder. Meanwhile, the old crook controls himself enough to caution Sikes against excessive violence — always having in mind the perils of a careless move.
There are some traces of human feeling left in Fagin's self-serving nature. On several occasions, he shows a trace of kindliness toward Oliver. On the night that he maneuvers Oliver into the Chertsey expedition, the old man checks his impulse to disrupt the persecuted child's sleep. The next day, he earnestly entreats Oliver to mind Sikes without question, for his own safety.