What is the conventional Renaissance conceit which Spenser uses in Sonnet 54 of Amoretti?
Sonnet 54 by Edmund Spenser:
Of this worlds theatre in which we stay,
My love like the spectator ydly sits
Beholding me that all the pageants play,
Disguysing diversly my troubled wits.
Sometimes I joy when glad occasion fits,
And mask in myrth lyke to a comedy:
Soone after when my joy to sorrow flits,
I waile and make my woes a tragedy.
Yet she, beholding me with constant eye,
Delights not in my merth nor rues my smart:
But when I laugh she mocks, and when I cry
She laughs and hardens evermore her heart.
What then can move her? if nor merth nor mone,
She is no woman, but a senceless stone.
Here, Spenser uses the conceit, or extended metaphor, of the "Theatre." Notice its corresponding analogies: "Comedy," "Tragedy," "mask," "pageants," "play," and "spectator." Notice also that we have a speaker (presumably male) and a female (presumably his lover). So, he is the actor on stage, and she is the spectator in the audience.
So as the theatre changes its venue between comedy and tragedy, so too does his lover. His lover is at first an "idle spectator," but then she mocks the performance. She laughs at his tragedies and cries at his comedies--all situational irony. In the end, the speaker says she is no woman, but compares her to a stone. So, she is idle at the beginning and the end of their relationship. Obviously, he needs to find a new venue for his love.