What is the most important issue in Pride and Prejudice?

Jane Austen's "Pride and Prejudice" raises important moral issues concerned with the central theme of the novel namely the institution of marriage and other important aspects associated with the institution of marriage.

Jane Austen belongs to the Romantic Age in English literature.

"Pride and Prejudice"(1813) like all of Jane Austen's novels reflects faithfully the socio-economic conditions of what historians term as 'Regency England'(1811-20).

Since women of this period had no right to ownership of property they were financially dependent on their husbands,and hence the urgency and anxiety throughout the novel for the ladies to get married to "young men of large fortune" (ch. 1).

Mr.Bennet's estate is 'entailed' to Mr. Collins because Mr.Bennet does not have a son. In 'Regency England' only male heirs could inherit the title and the estate of their fathers. The third paragraph of chapter 50 clearly reveals the 'economic' necessity of having a son and the disappointment at not being able to have one and the consequent predicament which Mr.Bennet faces in not being able to personally meet the financial demands of Wickham.

In Ch.33 Col.Fitzwilliam tells Elizabeth "I may suffer from the want of money. Younger sons cannot marry where they like." Clearly hinting at her impoverished status.

The central theme of the novel--how much money is necessary for a successful and a happy marriage--is explicitly stated by Elizabeth in in Ch.27 : "Pray, my dear aunt, what is the difference in matrimonial affairs, between the mercenary and the prudent motive? WHERE DOES DISCRETION END, AND AVARICE BEGIN?"

Was Col. Fitzwilliam Darcy 'discreet' or 'avaricious'?

The contrasting lifestyles of different social groups is structurally central to a Jane Austen novel. In "Pride and Prejudice" the landed gentry represented by Darcy  is contrasted with the newly rich trading class represented by Bingley and his sisters.

The novel was written against the background of the threat of an  invasion by Napoleon. The militia was a temporary voluntary force raised especially during times of a national emergency. Wickham was a member of this militia. Col.Fitzwilliam Darcy the younger son of an earl, on the contrary, is a fully commissioned officer of the regular army. In those days only an aristocrat or a member of the gentry could afford to purchase a commission in the army. In "Pride and Prejudice" Darcy purchases a commission for Wickham so that Wickham agrees to marry Lydia.

Jane Austen  portrays only the elegant aspects of Regency England. The seamy side,however, is  sometimes hinted at. Discipline in the army was very harsh and there is a report of a private being whipped. Similarly the prevailing poverty of the lower classes is revealed by the reference to poor feeding.

But most importantly the harsh reality of a bleak future  for a dependent unwed old woman is hinted at when Charlotte Lucas' brothers are relieved that Collins  is going to marry their sister, for otherwise they would have to look after her in her old age.