Who so blind as he that will not see?

The question suggests that someone who refuses to look can be harder to help than someone who cannot see. Figuratively, it describes a person who will not acknowledge what is plain to others.

Its force falls on unwillingness rather than lack of ability. The speaker implies that further explanation may do little good while the person remains determined to reject the facts.

Use it to criticize a refusal to recognize clear evidence or an uncomfortable truth, especially after the matter has been explained. Because it assigns blame, it can sound harsh when the person's understanding or motives are uncertain.