Who said There's none so blind as those who will not see?

The phrase "There's none so blind as those who will not see" is often attributed to John Heywood, a 16th-century English playwright and poet. It suggests that people who refuse to acknowledge the truth or reality are the most blind, even more so than those who are physically unable to see. The saying emphasizes the idea that willful ignorance can be more limiting than a lack of physical sight.