Ignorance more frequently begets confidence than does knowledge: it is those who know little, and not those who know much, who so positively assert that this or that problem will never be solved by science.

The only good is knowledge and the only evil is ignorance.

Ignorance is the curse of God; knowledge is the wing wherewith we fly to heaven.

You don't know what you don't know.

There is but one evil, ignorance.

All that I know is nothing - I'm not even sure of that.