What is the possible theme found in the novel which is supported by the motif of the changing characters name?

The fact that the characters consistently change their names directly relates to changes within the characters themselves. Dantès goes by a number of different names; he has a name for each role he plays throughout the novel. Believing himself to be an angel of justice, he takes on the persona of abbot (judgment); Lord Wilmore during moments of charity, and Monte Cristo when acting as the avenging angel he believes himself to be. Dantès' identities symbolize his lack of focus and inability to act on his own behalf. He needs to take on other identities to do what he cannot.