Our revels now are ended. These our actors, As I foretold you, were all spirits and Are melted into air, into thin air; And—like the baseless fabric of this vision— The cloud-capped towers, the gorgeous palaces, The solemn temples, the great globe itself, Yea, all which it inherit, shall dissolve, And like this insubstantial pageant faded, Leave not a rack behind. We are such stuff As dreams are made on, and our little life Is rounded with a sleep. ...—Prospero
The Tempest is explicitly concerned with its own nature as a play, frequently drawing links between Prospero's art and theatrical illusion; the shipwreck was a spectacle that Ariel performed, while Antonio and Sebastian are cast in a troop to act. Prospero may even refer to the Globe Theatre when he describes the whole world as an illusion: "the great globe ... shall dissolve ... like this insubstantial pageant". Ariel frequently disguises himself as figures from Classical mythology, for example a nymph, a harpy, and Ceres, acting as the latter in a masque and anti-masque that Prospero creates.
Early critics, such as Thomas Campbell in 1838, saw this constant allusion to the theatre as an indication that Prospero was meant to represent Shakespeare; the character's renunciation of magic thus signalling Shakespeare's farewell to the stage. This theory persists among later critics, and remains solidly within the critical canon.
Magic was a controversial subject in Shakespeare's day. In Italy in 1600, Giordano Bruno was burnt at the stake for his occult studies. Outside the Catholic world, in Protestant England where Shakespeare wrote The Tempest, magic was also taboo; not all "magic", however, was considered evil. Several thinkers took a more rational approach to the study of the supernatural, with the determination to discover the workings of unusual phenomena. The German Henricus Cornelius Agrippa was one such thinker, who published in De Occulta Philosophia (1531, 1533) his observations of "divine" magic. Agrippa's work influenced Dr. John Dee, an Englishman and student of supernatural phenomena. Both Agrippa and Dee describe a kind of magic similar to Prospero's: one that is based on 16th-century science, rationality, and divinity, rather than the occult. When King James took the throne, Dee found himself under attack for his beliefs, but was able to defend himself successfully by explaining the divine nature of his profession. However, he died in disgrace in 1608.
Shakespeare is also careful to make the distinction that Prospero presents himself as a rational, and not an occultist, magician. He does this by providing a contrast to him in Sycorax. Sycorax is said to have worshipped the devil and been full of "earthy and abhored commands". She was unable to control Ariel, who was "too delicate" for such dark tasks. Prospero's rational goodness enables him to control Ariel where Sycorax can only trap him in a tree. Sycorax's magic is frequently described as destructive and terrible, where Prospero's is said to be wondrous and beautiful. Prospero seeks to set things right in his world through his magic, and once that is done, he renounces it, setting Ariel free. Of course, the problem is, Prospero never actually does any magical acts. Only Ariel does. The magic of Prospero is a matter of language alone.
The Tempest can be interpreted as Shakespeare's last treatise on the human soul, in particular the Renaissance conception of the tripartite soul divided into vegetative, sensitive, and rational spheres, as described in Plato's tripartite theory of soul and Christian Philosophy. This was later also described in Sigmund Freud's id, ego and super ego which was first linked to The Tempest in the 1956 screenplay for Forbidden Planet by Cyril Hume, Irving Block, and Allen Adler. The film presents Caliban reinterpreted as the 'monster from the Id', although the theory is dismissed as 'obsolete' in that imagined future, and was also scholarly dismissed by James E Phillips in 1964. Prospero is exiled to an island with a symbol of his baser, 'vegetative' nature – Caliban – and his higher, 'sensitive' or supernatural side – Ariel. Some productions have seen the same actor play all three roles, making them symbols of the conflict within a fully actualised or awakened Prospero – that between crude selfish physicality and a higher, mystical side. In the screenplay for Forbidden Planet it is revealed that the id monster is an externalization of Dr Morbius' psyche.
For as long as Prospero is battling with these qualities and lost in books, he is banished from Milan. As the play finds its conclusion, he is both able to accept his base, brutal nature ("this thing of darkness I acknowledge mine" he says when taking responsibility for Caliban) while letting go of his connection with higher, powerful forces ("then to the elements be free, and fare thou well" he says, setting Ariel free). Abandoning magic and acknowledging the brutal potential of his nature, he is allowed to return to his rightful place as Duke, subject to agreement from the audience: "as you from crimes would pardon'd be, let your indulgence set me free."