Pros. [Aside] I had forgot that foul conspiracy Of the beast Caliban and his confederates Against my life:  the minute of their plot Is almost come. [To the Spirits.] Well done! avoid; no more.

     Fer. This is strange; your father’s in some passion
     That works him strongly.

     Mir. Never till this day
     Saw I him touch’d with anger so distemper’d.

     Pros. You do look, my son, in a moved sort,
     As if you were dismay’d:  be cheerful, sir. 
     Our revels....

And then, after the famous lines, follow these: 

                                Sir, I am vex’d: 
     Bear with my weakness; my old brain is troubled;
     Be not disturb’d with my infirmity;
     If you be pleased, retire into my cell
     And there repose:  a turn or two I’ll walk,
     To still my beating mind.

We seem to see here the whole mind of Shakespeare in his last years.  That which provokes in Prospero first a ‘passion’ of anger, and, a moment later, that melancholy and mystical thought that the great world must perish utterly and that man is but a dream, is the sudden recollection of gross and apparently incurable evil in the ‘monster’ whom he had tried in vain to raise and soften, and in the monster’s human confederates.  It is this, which is but the repetition of his earlier experience of treachery and ingratitude, that troubles his old brain, makes his mind ’beat,’[192] and forces on him the sense of unreality and evanescence in the world and the life that are haunted by such evil.  Nor, though Prospero can spare and forgive, is there any sign to the end that he believes the evil curable either in the monster, the ‘born devil,’ or in the more monstrous villains, the ’worse than devils,’ whom he so sternly dismisses.  But he has learned patience, has come to regard his anger and loathing as a weakness or infirmity, and would not have it disturb the young and innocent.  And so, in the days of King Lear, it was chiefly the power of ‘monstrous’ and apparently cureless evil in the ‘great world’ that filled Shakespeare’s soul with horror, and perhaps forced him sometimes to yield to the infirmity of misanthropy and despair, to cry ‘No, no, no life,’ and to take refuge in the thought that this fitful fever is a dream that must soon fade into a dreamless sleep; until, to free himself from the perilous stuff that weighed upon his heart, he summoned to his aid his ‘so potent art,’ and wrought this stuff into the stormy music of his greatest poem, which seems to cry,

     You heavens, give me that patience, patience I need,

and, like the Tempest, seems to preach to us from end to end, ’Thou must be patient,’ ’Bear free and patient thoughts.’[193]

FOOTNOTES: 

[Footnote 158:  Of course I do not mean that he is beginning to be insane, and still less that he is insane (as some medical critics suggest).]