"Pride," observed Mary, who piqued herself upon the solidity of her reflections, "is a very common failing, I believe. By all that I have ever read, I am convinced that it is very common indeed; that human nature is particularly prone to it, and that there are very few of us who do not cherish a feeling of self-complacency on the score of some quality or other, real or imaginary. Vanity and pride are different things, though the words are often used synonymously. A person may be proud without being vain. Pride relates more to our opinion of ourselves, vanity to what we would have others think of us."

– Jane Austen

Pride and Prejudice, Chapter 5. The girls are discussing Mr. Darcy and what they perceive to be his pride. Mary Bennet, who likes to philosophize and moralize, distinguishes between pride and vanity. She explains that pride is more about our opinion of ourselves and vanity how we would have others think of us. Both are major themes in the novel, and are evident in the characters of Elizabeth, Mr. Collins, Lady Catherine de Bourgh, as well as Mr. Darcy. Mary is showing off here, and so ironically displays the pride and vanity that she is preaching about in others.