‘The purpose of playing,’ says Hamlet, is ‘to hold as ‘twere the mirror up to nature: to show virtue her feature, scorn her own image, and the very age and body of the time his form and pressure.’ Hamlet himself employs ‘playing’, in various guises, as a means of penetrating false appearances to uncover hidden truths, but he also discovers how slippery illusions can be when their effects become entangled in the human world. Like Hamlet, but in a comic vein, Twelfth Night poses questions about ‘the purpose of playing’ and about whether illusion is perhaps too deeply embedded in human experience to be ever completely separated from reality.

Virtually every character in Twelfth Night is either an agent or a victim of illusion, and often a player will assume both these roles: as Viola is an impostor but also a prisoner of her own disguise, or as Sir Toby loses control of the deception he has contrived when he mistakes Sebastian for his twin. Illyria is a world populated by pretenders, which has led one critic to describe the action as 'a dance of maskers . . . for the assumption of the play is that no one is without a mask in the serio-comic business of the pursuit of happiness'. In the course of the story, many of these masks are stripped away or willingly set aside; but illusion itself plays a pivotal yet somewhat ambiguous role in this process.