The problem with appropriating characteristics to Sir Peter from Sheridan's play, The School for Scandal is that virtually all of the characters in this sentimental comedy/comedy of manners represent Sheridan himself with an unvarying wit that is so characteristic of the playwright.
However, since the characters in comedies of manners are usually stock characters, Sir Peter is depicted as the upright older gentleman who also has a certain wisdom. For example, he sometimes doubts his good judgment in marrying his young wife, who piques him with her wishes to visit the salon of Lady Sneerwell, who impugns the reputation of her society with her recreational malicious gossip.
When his young wife complains to her fatherly husband that he is depriving her of freedom, he lovingly acquiesces and accompanies her to Lady Sneerwell's. However, when he enters and hears all the malicious and libelous remarks, Sir Peter Teazel is appalled and swiftly departs. But, before he leaves, Sir Peter chastises the company, reminding them that ruining someone's reputation gratuitously is as wrong as poaching game from manors:
SIR PETER. 'Fore heaven! Madam, if they were to consider the Sporting with Reputation of as much importance as poaching on manors— and pass an Act for the Preservation of Fame—there are many would thank them for the Bill. [Act II, Scene 2]
Nevertheless, despite his refusal to be part of gossip and deception, Sir Peter becomes entangled in intrigue because of his good character that sometimes renders him somewhat naive. For instance, it is Sir Oliver who assesses the character of Charles and Joseph and reveals to Sir Peter Teazle the virtuous qualities of Charles.
Later,after a humorous scene in which Joseph has tried to seduce Lady Teazle and Sir Peter approaches so Lacy Teazle hides behind a screen, and Charles then enters, the hypocritical Joseph double-talks to the point that he is caught in his subterfuge, Sir Peter realizes that Joseph is deceptive and untrustworthy while Charles is forthright. He then treats the young men accordingly as he is an honorable man.