The theme of The Count of Monte Cristo is one of vengeance and forgiveness, power and powerlessness. When Dantes is unfairly given a life-prison sentence by his enemies (Villefort, Danglars, and Fernand), he spends every waking moment planning his revenge. As soon as Dantes miraculously escapes and returns to the world with riches, he sees it as a sign that God has opened for him the door of revenge.
No longer does the reader recognize the pre-prison Dantes. Fourteen years behind bars in a dark cell has given him a criminal's mind. Instead of the innocent, carefree, life-loving boy of nineteen, Dantes is now a hardened, cynical, and mistrustful man in his mid-thirties. It seems a reverse baptism of sorts takes place instantly as Dantes hits the water after being thrown off the cliff by the prison guards. Immediately Dantes begins lying to and using those around him. No longer is Dantes the clear-cut hero.
To reinforce this change, Dumas refers to Dantes as the Count of Monte Cristo once he returns to society. Now the count, not his enemies, plays games with those he dislikes. Though he rewards those who treated him and his father well, most of the story is devoted to Monte Cristo's desire for vengeance. Throughout the story, Dantes changes disguises in order to deceive those around him and further his own agenda of punishment for his enemies.
Yet when he sees Villefort's dead son, a truly innocent victim, the count realizes that he has gone too far. For the first time he comes to the realization that perhaps he doesn't have the gift of Providence, the right to punish others. In efforts to reconcile these feelings, Monte Cristo arranges the marriage between Maximilien and Valentine.
At first he hopes to punish himself by committing suicide, but when Haydee admits her love for him, the count takes it as a sign from God that he is forgiven. Monte Cristo concludes the book with these two parting quotes:
Count: "Tell the angel who will watch over your life to pray now and then for a man who, like Satan, believed himself for an instant to be equal to God, but who realized in all humility that supreme power and wisdom are in the hands of God alone."
Count: "Only a man who has felt ultimate despair is capable of feeling ultimate bliss."
These quotes underscore the themes of the entire novel:
1) God is always more powerful than man.
2) Only God has the right to punish and reward.
3) Only a man who knows deep sadness can experience true happiness.