* Misdirection: By calling him "Jacques," Barsad attempts to mislead Defarge into thinking he's on the side of the revolutionaries. He pretends to be a fellow revolutionary, gaining Defarge's trust and potentially extracting information.
* Intrigue: The constant use of the alias creates an air of mystery and tension. It underscores the spy's double life and the dangerous game he's playing.
* Foreshadowing: This repeated use of the alias foreshadows the eventual revelation of Barsad's true identity and his connection to the French aristocracy. It creates an unsettling feeling that something is amiss, prompting the reader to question his motives.
* Character Development: The use of the alias also emphasizes Defarge's strong sense of suspicion and his ability to read people. He is cautious about Barsad's intentions, even though Barsad uses a revolutionary pseudonym.
Ultimately, the alias "Jacques" is a tool used by Barsad to manipulate Defarge and further his own agenda, which is to infiltrate the revolution and protect the interests of the French aristocracy.