Responsibility
This is a major theme of Fred's story, and he must becomes responsible for his finances and his choices. Will does too, to a certain extent. Both men must learn how to rely on themselves, not infringe upon others, and how to become independent in many ways.
Stubbornness
A big issue of character. Rosamond is extremely stubborn, meaning that if things aren't done her way, she will go behind other people's backs to do things the way she thinks they should be done. Societal stubbornness is responsible for Lydgate's failure with his medical practice; people want what they want, for whatever reasons, which means that they are blind to things that might be best for them.
Prejudice
A theme that Lydgate and Will Ladislaw cannot seem to beat. People in Middlemarch dislike anyone who is not from Middlemarch, or anyone whose reputation seems questionable. Will and Lydgate are both good people, but it is initial prejudice, sometimes based on invalid or circumstantial reasons, that means that they are never liked or accepted in Middlemarch.
Conformity
An issue that is related to societal expectation, but is somewhat different. People are supposed to conform to certain social ideals and normsDorothea is supposed to be a proper wife and then a proper widow, and follow society's set guidelines about how to fill each position. Will fits no position that society tries to group him into, so he is disliked; he refuses to be conventional or proper, or to fit into that society and its ideas of how someone like Will should act.
Love
Love keeps people together, or the lack or it lets them drift apart. Those who are truly in lovelike Will and Dorothea, Mary and Fredare bound together by it, and are very alike in temperament and outlook. Those who lack itlike Lydgate and Rosamond, Casaubon and Dorotheaare ill-suited to each other in marriage, and are very disappointed by their unions.
Unity of Middlemarch
The decisions made by every person in Middlemarch seem to have a direct effect on at least one other person. Mary's decision to marry Fred means that Farebrother is without a wife. Dorothea's decision to choose Casaubon leads Sir James to choose Celia. Bulstrode's dirty dealings with regard to Raffles mean disgrace to both Lydgate and Will Ladislaw. Everyone in Middlemarch is intimately connected, and it seems that no one can move around without disturbing someone else.
Societal Expectations
Closely linked to society's hierarchy, are ideas about how everyone should act in certain situations. Lydgate proposes to Rosamond because society expects that he should do it. Dorothea is pushed to live with someone else or marry again after she is widowed, because society expects that it is right. People don't necessarily follow these expectations, nor should they; but they do exist, and play a part in people's lives.
Vanity
Especially relevant to Rosamond and her suitors. Rosamond is exceptionally vain about her charm and her appearances, so much so that it is a shock to her when her friend Ladislaw says he doesn't love her. Her unsuccessful suitors are all equally vain, and blame Lydgate, rather than Rosamond's lack of interest, when she won't return their favor.
Self-discovery
There are certain truths which every character learns about himself in the course of trials; Lydgate and Rosamond find out more about their characters through their money troubles, though they do not always adjust accordingly. Dorothea makes the most dramatic journey of self-discovery, and changes a great deal within the course of the novel.
Reality vs. Expectations
Many characters' preconceived ideas, especially of marriage, are proven tragically wrong in the course of the book. Casaubon and Dorothea both have unrealistic ideas about marriage, and are disappointed. Lydgate and Rosamond have the same idea, and are let down. Life often defies what one expects, or could predict of it; and the people who are happiest are the ones who have few expectations, or are most flexible.
Conscience vs. self-interest
This is a question that comes to play in Lydgate's life in particular. Does one do what one thinks is right, or what gives one the most benefit? Lydgate often goes for self-interest, though it gets him into trouble.
Gender roles and expectations
Especially relevant to Dorothea. Middlemarch society has very defined ideas of what people of each gender should do within the society, and people, especially women, who deviate from this norm, are looked down upon. Dorothea is tolerated because she is of good family and does not disrupt the society she is in. However, she faces a great deal of pressure to change herself, conform to others' ideas, and submit herself to male leadership at all times.
Progress
Much is changing in the world of Middlemarch; English society is evolving in social, economic, technologic areas. Socially, ideas of gender and class are in flux, as women are proving more and more competent, and the Industrial Revolution is causing a greater amount of social mobility. The economy of England is changing, from an aristocratic, inheritance- based system of holding wealth and land, to one based on commerce, business, and manufacturing. Technology is also changing, in medical science, and in areas like transportation, and these are changes that are beginning to sweep through Middlemarch.
Pride
This is something which both helps and hinders many people in the book, and is most applicable to Dorothea, Will Ladislaw, and Lydgate. With Lydgate, pride is a tumbling block, something that keeps him from putting his affairs in order, and sometimes doing what is necessary in his marriage and practice. Dorothea and Will's pride is more involved in who they are personallyneither of them likes to be regarded poorly, will defend themselves and their decisions if needed, and follow their own course with regards to everything.
Money
Money is the root of many evils, but much good, in the novel. Lydgate gets desperate for want of it, Fred despairs when he has little, Dorothea becomes generous when she has too much, and the Garths save carefully since their money is limited. Money has a profound effect on character within the novel, and though many people are judged by how much money they have, many of the best people in the novel, like Will Ladislaw and Mr. Farebrother, have very little.
Strength of rumor
Rumor can do a great deal of damage in Middlemarch, having even more weight than fact in some cases. Both Bulstrode and Lydgate are blackened by rumors passed around society, and Will is blackened as well, though he is falsely accused.
Politics
Everything is political in Middlemarch, with most people strongly backing the conservative party. Personal alliances and aversions are based on matters of politics and political identification. But even political matters, like all things, get personal; people decide who or who not to support by how they like them, even more so sometimes than any dependence on issues.
Family obligation
People within the novel have varying ideas of family obligation in the novel, though it is a strong force in Middlemarch society. Mr. Featherstone's relations believe they are entitled to money; Mrs. Bulstrode believes that she must help and advise her family in order to show support. Sir James shows his regard for his family by being very protective and a constant advisor as well. Casaubon dispenses of his obligation through money, and Bulstrode attempts also to do the same.
Social position
Social position means a great deal in Middlemarch; it means how much respect a person gets, how people treat them, how they are regarded, etc. People of high status are generally treated more delicately than people with little money, like Lydgate and Will Ladislaw. Birth and connections are also important in determining a person's place, and also what benefits they will receive from society.