Don't be afraid to study hard: knowledge never exhausts the mind.

Only knowledge and truth may result in freedom of mind.

Inside the human mind, an idea is a mental spark that occurs as a response to the challenge of a train of thought.

An idea occurs in the mind, where it is confined and useless. An idea lives when it leaves the mind.

An unsolved problem bothers one's mind, just as a small stone in the shoe,until an idea for solving the problem comes to mind.