"Plain" is a symbol of the absence of obstacles to the knowledge and realization of God's Commandments, an image of spiritually peaceful state of righteous life of man, acquired by his constant fulfillment of God's Will, His Covenants, Commandments.

Negative Meaning.

"Plain" is a symbol of the state of man living a stagnant, spiritless, inactive, sinful way of life, in a state of lack of spiritual height of knowledge and fulfillment of the Will of God.