What are two internal and external conflicts of the main character?A Tale of Two Cities by Charles Dickens

A common criticism of Charles Dickens's A Tale of Two Cities is that many of the characters are undeveloped.  Even Sydney Carton, considered the main character, lacks the introspection that is frequent in such important characters.  In addition, the reader knows little of his past.  However, as the main character, he does experience conflicts.

EXTERNAL CONFLICTS

1.  As the "Jackal," Sydney is exploited by the "Lion," C.J. Stryver who uses his brillant mind to win legal cases.  Stryver also mocks Carton as he forces him to work long hours into the night.  In Chapter 5 of Book the Second, Styrver ridicules Carton:

'The old Sydney Carton of Shrewsbury School....the old seesaw Sydney.  Upon one minute and down the next; now in spirits and now in despondency.'

2.  In Book the Third Sydney Carton comes into contact with the spy John Basard, whom he has learned from Jerry Cruncher has used the alias of Roger Cly in England.  He is the "witness" to Charles Darnay's purportedly treasonous remarks about the King.  Since Jerry has told Carton that this spy faked his death as Cly, Carton uses this information to coerce Basard, who is involved with the incarceration of the prisoners in France, to allow him to switch places with Charles Darnay and allow Darnay to leave the prison.

INTERNAL CONFLICTS

1.  Sydney Carton is a man with great potential as he has a brillant mind.  But his dissipation and self-deprecatory nature will not allow him to succeed.  Although he loves Lucie, his feeling of inferiority regarding Charles Darnay prevent him from competing for her love. After his evening with Darnay, Carton looks at him in a mirror asking himself,

'Do you particularly like the man?...why should you particularly like a man who resembles you?  There is nothing in you to like; you know that. (Bk.II,ch.4)

With this sense of inferiority, Carton resigns himself to being allowed to be Lucie's friend.

2.  This sense of lack of accomplishment in life--"summoning no energy and purpose" as Stryver tells him--and his depression keep Sydney from making anything of himself.  Disturbed that his life has been worthless, Sydney seeks to achieve something worthwhile.  Thus, his act of sacrifice will, he hopes, redeem his worthless life:

'It is a far, far betting thing that I do, than I have ever done....'