There are sayings, to ponder from your innermost heart, give from your heart or listen from your heart, implying that the heart is pure, or was originally pure. Some may call this heart the soul of the individual, an intangible collection of positive and negative energy.
But the mind that creates evil thoughts pollutes the heart (soul), and hardens the heart (soul) with negative energy. The person who has this heart is considered evil by society. A person that creates positive thoughts has a pure heart and considered light hearted and spirited.
But even the most evil person in the world once had a pure heart. It is only because evil (greed, arrogance, and self love) thoughts have penetrated his heart, that his soul is hardened. This soul is said to be weighted down by evil; and sinks to the bottom, making it easy for God’s judgment.
In essence human beings are meant to have pure hearts. We are influenced by our environment in causing the mind to produce evil or positive thoughts. It is with this reasoning, that we must teach people to eliminate greed, arrogance from their minds. When this happen, their hearts (souls) will be lightened and spirited.