According to Chih-i’s theory of one mind embracing three thousand dharmas (I-nien San-ch’ien), the mind of a single sentient being contains Ten Dharma-realms. Why? The Ten Dharma-realms are the manifestation of the True Reality. Considering that sentient beings originally possess True Reality (i.e., the real nature of entities), the Ten Dharma-realms that are the manifestation of the True Reality are likewise present everywhere and are contained in the minds of sentient beings. An evil thought belongs to the worlds of hell-dwellers, hungry ghosts, and animals; a good thought belongs to the worlds of human and heaven beings; and a thought of compassion belongs to the realm of the bodhisattva and the Buddha. Obviously, it would not be possible for different Dharma-realms to be manifest if one’s mind did not contain all of the Ten Dharma-realms. On the one hand, one instant thought includes the whole universe, and one dharma is identical to all dharmas. On the other hand, the whole universe only exists in every single thought, whereby all dharmas are identical to one dharma. Chih-i’s theory is that the reason one’s thought corresponds to a certain realm at a certain moment signifies that one good thought designates the manifestation of virtue and concealment of evil, and one evil thought the manifestation of evil and concealment of virtue. Good and evil are one entity, and the difference lies in the state between manifestation and concealment. Good and evil transform according to conditions, which is similar to the relationship between ice and water. This indicates that both aspects exist as the one entity of True Reality, which arises in turn with causes and conditions. (Vol. 2, Page 252-253)