Here's a breakdown of what it likely means in the context of the chapter:
* Charles Darnay's inner turmoil: At this point, Darnay is struggling with the knowledge of his family's past and the potential consequences of his actions. He is torn between his loyalty to his family and his commitment to his new life in England, particularly his love for Lucie Manette. The "state of his heart" reflects this internal conflict and the heavy weight of his responsibility.
* His struggle with secrets: He is keeping a secret about his identity and past, which is causing him immense stress and guilt. The phrase "state of his heart" indicates the deep emotional toll this secret is taking on him.
* His desire for honesty and redemption: Darnay is seeking to be honest and transparent, but he fears the consequences of revealing his true identity. His "state of his heart" expresses his longing for redemption and his desire to be free from the burden of his past.
In essence, the "state of his heart" is a powerful image that emphasizes the internal struggles and anxieties of Darnay, highlighting his vulnerability and his yearning for a clear conscience.