He is not only dull himself, he is the cause of dullness in others

He is not only dull in himself, but the cause of dullness in others.

He was dull in a new way, and that made many think him great

Dullness is the enemy.

To believe is very dull. To doubt is intensely engrossing.

If you are idle, be not solitary; if you are solitary, be not idle