"Men are four; He who knows and knows not that he knows. He is asleep; wake him. He who knows not and knows not that he knows not. He is a fool; shun him. He who knows not and knows that he knows not. He is a child; teach him. He who knows and knows that he knows. He is a king; follow him. The heights by great men reached and kept Were not attained by sudden flight, But they, while their companions slept, Were toiling upward in the night."

Source: Henry Wadsworth Longfellow (2013). “Delphi Complete Works of Henry Wadsworth Longfellow (Illustrated)”, p.1522, Delphi Classics