| Quote #4
Here, Feste points out that foolishness is a relative term when Olivia asks her "Fool" to look after the drunken and passed out Sir Toby Belch.
| Quote #5
It's true that Feste is a professional Fool, but the play seems pretty intent on demonstrating that he is also the wisest figure in the play. Here, he deftly shows Olivia why she, not him, is irrational in her love for a dead brother.
| Quote #6
When Feste says Orsino ought to wear a "taffeta" doublet, he gives voice to the idea that Orsino is moody, fickle, and silly. (Taffeta is a fabric woven of various colored threads, which gives it an iridescent quality that changes color depending on the angle at which it's viewed.) If Orsino were to wear a taffeta coat, his costume would match his "changeable" mind, which has been made "melancholy" by the Duke's obsession with love. Shakespeare beats us over the head with the idea that love, especially the Duke's self-love, is utterly ridiculous.