The sole drift

Ariel. Your charm so strongly works 'em,
That if you now beheld them, your affections
Would become tender.

Prospero. Dost thou think so, spirit?

Ariel. Mine would, sir, were I human.

Prospero. And mine shall.
Hast thou, which art but air, a touch, a feeling
Of their afflictions, and shall not myself,
One of their kind, that relish all as sharply,
Passion'd as they, be kindlier moved than thou art?
Though with their high wrongs I am struck to the quick,
Yet with my nobler reason 'gainst my fury
Do I take part: the rarer action is
In virtue than in vengeance: they being penitent,
The sole drift of my purpose doth extend
Not a frown further. Go release them, Ariel.
My charms I'll break, their senses I'll restore,
And they shall be themselves.