Quote 1
She was the golden thread that united him to a Past beyond his misery, and to a Present beyond his misery: and the sound of her voice, the light of her face, the touch of her hand, had a strong beneficial influence with him almost always. (2.4.3)
Lucie becomes a conduit for Doctor Manette’s own experiences. Deprived of his life in prison, he begins to live through her.
Quote 2
"Charles Darnay, mysteries arise out of close love, as well as out of wide division; in the former case, they are subtle and delicate, and difficult to penetrate. My daughter Lucie is, in this one respect, such a mystery to me; I can make no guess at the state of her heart." (2.10.59)
Doctor Manette emphasizes the distance that can exist between even the closest of family members—a theme that the narrator himself later explores.
Quote 3
The faintness of the voice was pitiable and dreadful. […] Its deplorable peculiarity was, that it was the faintness of solitude and disuse. It was like the last feeble echo of a sound made long and long ago. (1.6.6)
Doctor Manette’s time in prison has robbed him not just of time but of his ability to re-enter the world, as well. Even his voice seems to have been forgotten.
Quote 4
What private solicitude could rear itself against the deluge of the Year One of Liberty—the deluge rising from below, not falling from above, and with the windows of Heaven shut, not opened! (3.4.8)
The rallying cry of "Liberty" becomes blind to the struggles and the rights of individuals. As everyone tells Doctor Manette, individual sacrifices for the good of the Republic should be welcomed—even if those sacrifices include the unfair execution of family members.
Quote 5
While one external cause, and that a reference to his long lingering agony, would always—as on the trial—evoke this condition from the depths of his soul, it was also in its nature to arise of itself, and to draw a gloom over him, as incomprehensible to those unacquainted with his story as if they had seen the shadow of the actual Bastille thrown upon him by a summer sun, when the substance was three hundred miles away. (2.4.2)
Doctor Manette’s imprisonment actually refines some of his most noble qualities. His experiences may be incommunicable, but they’ve also made him into a man of incredible strength.