Performance is central to Shakespeare's poems, not merely because the world's most famous man of the theatre was a major poet, but also because, by illuminating the vexed but neglected question of agency, it elucidates the ethical as well as the political dimensions of these poems. In the twentieth century, attention to the theatrical context of Shakespeare's poetry waxed and waned. Critics who emphasized the dramatic nature of the Sonnets especially in the middle part of the century were overtaken by those who insisted on reading the poetry against performance: for their wordplay; their exploration of the consciousness of private experience; the invention of a modern, poetic subjectivity; or the dynamics of a voice internalized by the solitary reader. More recently, however, commentators have restored both the theatrical and linguistic aspects of performance to the poems. The lyrical or narrative modes of a long poem or a sonnet may be performative in three different senses: (1) 'dramatic', if it uses the representative modes of drama, conveying the embodiment, enactment or expression of events, attitudes, or feelings, rather than merely describing them; (2) 'rhetorical', if it uses rhetorical devices to evoke emotions or attitudes or even prompt particular forms of action or behaviour; and (3) 'transformative', if it mobilizes the performative force of speech acts to act upon or change the world.

The first two are well known. The third, in which language is used to transform the world, needs some explanation. Transformative speech acts are neither true nor false, but rather effective or ineffective in accordance with pre-existing conventions. The force that they put into effect is often ethical or political. When I use a performative speech act like a promise, I am committing myself to a future act. And I commit myself in the act, in saying the words, ‘I promise . . .’ This act itself is public rather than private. It does not matter what I feel or even what I intend inwardly for me to be bound by the public act of my promise. Even if I make a promise with the inward intention of breaking it, I am still bound by my undertaking.