the transcription of Carton's final words are actually what he was thinking before dying and what he would have put down on paper had he been given the chance.

At any rate, Carton's last testament regards the future. He sees the revolutionaries eventually consumed by their own hate and paranoia, themselves dying under the guillotine's blade. He sees Paris restored to civility and peace. He also sees the Darnays naming one of their children in his honor and the child growing up to become the kind of man that Carton could have been but never was because of his alcoholism. He sees Dr. Manette respected, loved, and in peace as he passes away. He sees Charles and Lucie dying of old age, faithful to one another until the very end. Finally, he closes out his life with this famous statement:

It is a far, far better thing that I do, than I have ever done; it is a far, far better rest that I go to than I have ever known.

In essence, Carton is saying that his act of sacrifice has redeemed the waste that has been his life. He does not fear death because he knows that he is dying for a good cause and because he believes that he will find the ultimate peace in death.

Charles Dickens’ novel, A Tale of Two Cities, like most of his work, contains a number of complex and deeply drawn characters, including Sydney Carton. In A Tale of Two Cities, Dickens creates and develops a theme of regeneration. France, at least as far as the common man is concerned, is regenerated through revolution. Dr. Manette is regenerated by the love of his daughter Lucy. And Sydney Carton, at first despicable, drunken, and hopelessly narcissistic, is regenerated by own feelings and love for Lucy.

The quotation in your question occurs as Carton is sacrificing his own life in place of Charles Darnay, Lucy’s husband. Carton considers himself to have been “saved,” in a manner of speaking, by Lucy because she restored his appreciation of life. He expresses this appreciation to her a little earlier, in chapter 13:

I wish you to know that you have been the last dream of my soul. In my degradation I have not been so degraded but that the sight of you with your father, and of this home made such a home by you, has stirred old shadows that I thought had died out of me. 

Since he has no hope of having Lucy for his own, he expresses his love for her in the ultimate sense, by sacrificing his own life for her happiness and well being. It is this selfless act that connects A Tale of Two Cities to the great events in mankind’s history that required such devotion to move humanity forward.

The poignant last line of Sydney Carton, words that echo those of Jesus Christ who said,

Greater love hath no man than this, that a man lay down his life for his friends. (John 15:13)

declare the theme of redemption as well as vindicate the dissipated man, Sydney Carton, who so loves a woman that he will do anything to protect her. 

The scene of Carton climbing to his execution, redeemed from his dissipated ways as he sacrifices this life so that his beloved Lucie can live happily with her husband and child, places Sydney Carton as a Christ-like figure.  While there is the hope of redemption for Carton, the hope that he will be remembered fondly, he still makes the ultimate sacrifice, just as Christ has done.  Many a reader recognizes the heroism of Carton and is touched emotionally by this last passage.  As in the great Greek tragedies, Carton's actions evoke much sympathy and pity for Sydney Carton.