fluidity of gender, and in particular, the distinction between “boy” and “man” which is played out through the characters of Sebastian and Viola. Galen’s single-sex model of human anatomy was generally accepted in contemporary times, and asserted that “male” and “female” are points along a single spectrum in which the “male” is the superior. Genitalia was thus deemed homologous, with the female genitalia accepted as the inverted male phallus. Unlike the two-sex theory that developed around the 18th century and saw “male” and “female” as polar opposites, the one-sex model, in theory, offered progression towards the “male”. This is important when considering the feminine impression that Sebastian seems to give off to the other characters in Twelfth Night. The blind acceptance of Viola as Cesario suggests that “male” and “man” do not necessarily correlate, but require a “becoming”. For the entirety of the play, none of the characters doubt “Cesario’s” sincerity, and this, coupled with Orsino’s anaphoric exclamation, ‘One face, one voice, one habit, and two persons!’ (5.1.213-4), when the twins are stood together, serves to reinforce the other characters ignorance to the situation, but also the femininity of Sebastian. After Malvolio’s first interaction with Viola, who is under the guise of Cesario, he proclaims that Viola is ‘not yet old enough for a man, nor young enough for a boy’ (1.5.149), stuck in a limbo that conflates gender and anatomical sex as one in the same. This discussion hinges on Orsino’s statement seen above, and his insistence that they share ‘one face, one voice’ implicates Sebastian with all the gendered language and imagery that has surrounded the ‘eunuch’ (1.2.54) “Cesario” throughout the play. In Act 1, Malvolio says that Viola ‘speaks very shrewishly. One would think his mother’s milk were scarcely out of him’ (1.5.154), his description of Viola’s speech as shrewish, a word commonly associated with women, and the connection of Cesario with mother’s milk bears no sense of forceful renaissance masculinity. Olivia’s inquiry of ‘what kind o’ man is he?’ (1.5.143) consciously interrogates the relations