Every performer dreads an audience that simply will not react. In Sonnet 54, from his sequence *Amoretti*, Spenser takes the familiar idea that the world is a stage and shrinks it to one seat, occupied by the woman the speaker loves. She "ydly sits / Beholding me that all the pageants play": he performs every part while she watches. The central idea is a lover's complaint dressed as theatre. However many emotions he puts on display, nothing he does can move her.
The conceit is neatly divided. The first quatrain sets the scene, the second gives his two repertoire pieces, and the third gives her reaction. Joy becomes a comedy, in which he will "mask in myrth", and sorrow becomes a tragedy, in which he will "waile and make my woes a tragedy". The verbs are telling. "Mask" and "make" suggest the feelings are partly manufactured, as if the lover knows he is putting on a show to win a response. The phrase "Disguysing diversly my troubled wits" points the same way: judging by the line, the real turmoil lies underneath, and the costumes only give it different shapes. Even the word "ydly" works twice, since she is idle in the sense of being at leisure, and perhaps also in the sense of being useless to him. A good audience is supposed to be moved by what it sees, which makes her blankness a kind of failure of her role.
Sound and rhythm reinforce the sense of an actor's quick changes. The lines are regular iambic pentameter, steady like a stage routine, but the vocabulary is light and fast: joy "flits" into sorrow, and "Soone after" marks how little time passes between moods. The rhymes help. The first two quatrains are chained by the same "-its" sound (*sits*, *wits*, *fits*, *flits*), so the emotional switches feel tightly linked, one tumbling into the next. In the third quatrain the pattern breaks away to new rhymes, *eye* and *cry*, *smart* and *heart*, as if the poem has left the performance behind and moved on to her.
That third quatrain is where the poem sharpens. Her "constant eye" sounds like a compliment, since constancy is normally a virtue in love, but here it means a gaze that never wavers or warms. The poem also quietly escalates. She first "Delights not in my merth nor rues my smart", which is mere indifference. Then the syntax turns into a mirror image: "when I laugh she mocks, and when I cry / She laughs." The line break after "cry" delivers her laughter like a slap at the start of the next line. By the end of the quatrain she "hardens evermore her heart", and the stretched word "evermore" makes the hardening feel permanent. The repetition of "beholding" in lines 3 and 9 adds to the effect, because she is always the one who watches and he is always the one who is watched.
The couplet makes the hardening literal. "What then can move her?" is a real question, and also a pun. In theatre, to "move" an audience is to stir its feelings, but a stone can be moved only by force, so the word pushes toward the final image. The "nor... nor" structure shuts both routes, "merth" and "mone", and the verdict comes in blunt monosyllables: "She is no woman, but a senceless stone." The heavy final word lands like something dropped, and "senceless" means both without feeling and without senses, as though she were not even watching.
The sonnet matters because it takes a well-worn convention of love poetry, the unfeeling beloved, and gives it a structure that makes the problem visible. We can see the actor, the roles and the dead house. It also has a wry edge. The speaker's accusation is itself a performance, aimed at us as a third audience, and this one may be easier to move than she is. Spenser lets him be wounded and a little theatrical at once, which makes the lover more human than the stock suffering figure of many sonnets.