Analyze the following passage from School for Scandal and explain in as much detail as possible how and why this passage illustrates a dominant theme of the text. Use critical reasons to support your claim. Do not give a plot summary of the events surrounding the passage or rely upon broad generalization. SIR PETER: But here comes my helpmate. She appears in great good humor. How happy I should be if I could tease her into loving me, though but a little. (3.1.186–9)

The passage referenced in your question is in reference to the constant marital struggle between Sir Peter Teazle and his wife, Lady Teazle. In this quote, Sir Peter is expressing his frustration that his wife is always dissatisfied with him, hoping that she would instead be kind to him as he desires.
This quote illustrates an important thematic idea explored throughout the play; this theme is the idea of sentiment. Published during the eighteenth-century period of sentimentalism, the play suggests that men should exhibit the values of love, loyalty, and charity. Sir Peter represents this type of man inwardly, since these are the things he desires. That is why he is so upset that his wife is quarrelsome; he also fears that the rumors about her affair are true. Each of these aspects of their relationship seem to violate Sir Peter's principles.
This quote, then, demonstrates Sir Peter's heart; he wants his wife to exhibit the same values he holds dear, even though he is somewhat unable to exhibit them outwardly in her presence. Therefore, one could certainly argue that this quote highlights the theme of sentimentalism.