From The Works of William Shakespeare. Vol. 16. Ed. Evangeline Maria O'Connor. J.D. Morris and Co.
The Countess Olivia forms a pendant to the Duke; she, like him, is full of yearning melancholy. With an ostentatious exaggeration of sisterly love, she has vowed to pass seven whole years veiled like a nun, consecrating her whole life to sorrow for her dead brother. Yet we find in her speeches no trace of this devouring sorrow; she jests with her household, and rules it ably and well, until, at the first sight of the disguised Viola, she flames out
into passion, and, careless of the traditional reserve of
her sex, takes the most daring steps to win the supposed
youth. She is conceived as an unbalanced character,
who passes at a bound from exaggerated hatred for all
worldly things to total forgetfulness of her never-to-be-
forgotten sorrow. Yet she is not comic like Phebe; for Shakespeare has indicated that it is the Sebastian type,
foreshadowed in the disguised Viola, which is irresistible
to her; and Sebastian, we see, at once requites the love
which his sister had to reject. Her utterance of her passion, moreover, is always poetically beautiful.
Yet while she is sighing in vain for Viola, she necessarily appears as though seized with a mild erotic madness, similar to that of the Duke: and the folly of each is parodied in a witty and delightful fashion by Malvolio's entirely ludicrous love for his mistress, and vain confidence that she returns it. Olivia feels and says this herself, where she exclaims (iii. 4) —
"Go call him hither. — I am as mad as he
If sad and merry madness equal be."