Reflections on Sight and Vision
Losing his sight at a young age made Milton really interested in the meaning of sight—and we're not just talking about literal sight here either. In this poem, an account of a "vision," the ability to actually see, to discern physical characteristics, becomes less important than spiritual vision.
That vision encompasses not just the speaker's ability to discern his wife's spiritual qualities in her person, but his hopes for the afterlife and his trust in God's salvation. All of this spiritual vision leads to a paradox that's classic Milton—a blind speaker becomes a visionary.