Another similarity between Book I and Book III is the use of a House (castle) to represent a particular virtue or vice or a group of several. Here in Canto ii, we have the House of Joyeous (joyfulness), which does not seem like anything bad or immoral. We see, though, that the place has a most un-Christian joy: the joy of carelessness and the indulging of pleasures. Malecasta, appropriate to her name--which literally means "badly chaste"--is the opposite of Britomart, just as Duessa was the opposite of Una. Her "love" is nothing but physical desire; mistaking Britomart for a man, "her fickle hart conceived hasty fire...she was given all to fleshly lust, / And poured forth in sensuall delight (III.i.47-48)." Spenser makes fun of Malecasta's "fickle hart" by having her accidentally fall for another man--she is so fast, she doesn't even wait for a knight to get out of his (or her) armor.
It is a sign of Britomart's innocence that she does not immediately see Malecasta's desire for what it truly is. Likewise, her vision is clouded by the sight of Arthegall in her father's mirror; rather than rejoicing that she will have such a fine husband, she frets over the new feeling in her heart. She misinterprets it "Yet [she] thought it was not love, but some melancholy (III.ii.27)." Glauce, her nurse, tries to comfort her, saying, "For who with reason can you aye reprove, / To love the semblant pleasing most your mind, / And yield your heart, whence ye cannot remove (III.ii.40)." That is, love is in accord with reason, is not tainted by lust, and is fated anyway, so why resist it? Britomart resists because she cannot admit that any feeling so strong can still permit chastity; this negative view of the virtue is what she must change in the course of the Book.