Chapter 18 of the novel Pride and Prejudice takes place at the Netherfield ball, where Elizabeth is looking for Wickham, her recently acquired friend, only to find out that he is not there.
Elizabeth suspects that the feud between Mr. Wickham and Mr. Darcy has led the latter to ask his friend, Mr. Bingley, to omit Mr. Wickham from the list of guests, who are all red coat officers.
This helped confirm Elizabeth's assumption that Mr. Darcy was unfair and mean to Mr. Wickham, firing her hatred for Darcy even more. Additionally, she gets into a confrontation with Miss Bingley, in which Elizabeth is again told that Mr. Wickham's reputation is questionable.
As a result, Elizabeth goes to her sister, Jane, who isBingley's love interest. Bigley is also Mr. Darcy's best friend. Elizabeth needed confirmation from Jane as to whether she has heard anything negative about Wickham from Bingley.
However, Jane responds in the negative stating:
"Mr. Bingley does not know the whole of Wickham's history, and is quite ignorant of the circumstances which have principally offended Mr. Darcy; but he will vouch for the good conduct, the probity, and honour of his friend,.."
The term "probity" refers to Darcy's character and integrity. Basically what she said was that, although Bingley was not familiar with the feud between Darcy and Wickham, he does not question Darcy's choice, for he is a man with a flawless character and a high sense of integrity. Hence, Wickham probably deserves what he gets.