I perceive these lords
At this encounter do so much admire
That they devour their reason and scarce think
Their eyes do offices of truth, their words
Are natural breath.
– William Shakespeare
The Tempest, Act 5, Scene 1. Prospero comments on how Alonso and his party during their time on the island have lost their ability to think clearly and cannot see the truth. That is why they cannot believe their eyes and are speechless when they see the usurped duke Prospero in the flesh in the final act of The Tempest.