In act 1, scene 3 of Twelfth Night, Sir Toby Belch converses with his friend Sir Andrew Aguecheek. Sir Toby’s niece Olivia is single and wealthy, so she has many suitors, one of whom is Sir Andrew. In this scene, he is complaining to his friend that Olivia does not seem amenable to his courtship. Sir Toby enjoys Sir Andrew’s company in that the two like to drink together, and he has a higher opinion of his friend than other people do. Olivia’s maid Maria, for example, had earlier called Sir Andrew “a foolish knight”; Sir Toby responded by praising his wealth and accomplishments in music and language.
As the two men talk, Sir Toby comments that Sir Andrew seems a bit down and wonders what is bothering him. They exchange a few lines about food and drink, Sir Andrew opines that he has as much wit, meaning intelligence, as the next man but wonders if eating beef harms his wit. He shares that he is thinking of going home the next day. The reason is that Olivia is not receiving him. (She claims to still be in mourning for her late brother.) He takes this refusal as a sign that she will rebuff him as a suitor. He also believes that he cannot compete with Duke Orsino.
niece will not be seen. Or if she be, it's four
to one she'll none of me. The count himself
here hard by woos her.
Sir Toby replies,
She'll none o' the count. She'll not match
above her degree, neither in estate, years,
nor wit. I have heard her swear 't.
He means that Olivia does not intend to marry Duke Orsino or any other man she deems to be of superior status to her, whether in wealth or property, age, or intelligence. He is encouraging Sir Andrew to persevere in his courtship.