If ignorance is bliss, there should be more happy people in the world.

"Tain’t what a man don’t know that hurts him; it’s what he knows that just ain’t so."  – Frank McKinney Hubbard

An ignorant person is one who doesn’t know what you have just found out.

"I would rather have my ignorance than another man’s knowledge, because I have got so much more of it."  – Mark Twain

A man doesn’t know what he knows until he knows what he doesn’t know.

"Discussion is an exchange of knowledge; argument an exchange of ignorance."  – Robert Quillen

"Genuine ignorance is profitable because it is likely to be accompanied by humility, curiosity, and open mindedness; whereas ability to repeat catch-phrases, cant terms, familiar propositions, gives the conceit of learning and coats the mind with varnish water-proof to new ideas."  – John Dewey