Swamiji in Class 226 of Bagawat Geeta:

There are four types of people:

1. He who knows not and not knows knows not; fool
2. He who knows not and who knows knows not; ignorant; teach him
3. He who knows and knows not he knows; very intelligent but does not know he is intelligent; wake him
4. He who knows and knows he knows; very intelligent; follow him.

Vedas add one more variety – tamasic –  he who knows not and thinks he knows.