[W]hereas in Christianity arguments concerning the problem of evil focus on the relation of God and evil, in Tiantai it is the relation of Buddha and evil that is discussed. There arose a theory that there is evil in the Buddha, which proved controversial in later years. The idea that there is evil in the Buddha developed from the idea of the mutual inclusion of the ten worlds. In the idea often worlds, the world of the Buddha, as the world of supreme good, is located at the highest level, and the world of supreme evil, hell, is located at the lowest level. Human beings are in a middle position, caught between good and evil. Humans are intermediate beings, as emphasized in Western philosophy. But Tiantai insists that each of the ten worlds includes all of the others. Thus the world of the Buddha includes the supreme evil of hell. From this came the idea that there is evil in the Buddha, called “the theory of inherent evil.”

We can see the theoretical development of this idea in Tiantai’s The Profound Meaning of the Guanyin Chapter, according to which the Buddha does not intentionally do evil (cultivated evil) but includes evil in his nature (inherent evil). Here is, accordingly, the possibility of redeeming evil. Those who do not know evil are not qualified to redeem it. If we turn this theory of inherent evil around, it becomes possible to say that there is good, inherent good, in hell. From the idea of the mutual inclusion of the ten worlds, it follows that hell includes the supreme good of the Buddha’s world. Thus Tiantai taught the idea that there is good naturally even in hell. In this way, Tiantai recognized that hell would someday be awakened to the good, thus being redeemed and brought up into the Buddha’s world.

Put succinctly, evil and good are not permanently fixed in extreme contrast with each other. In this sense, the theory is authentically nondual. Stated positively, good and evil have things in common. The Profound Meaning of the Lotus Sutra says, “The nature and form of evil is really the nature and character of good. There is good because there is evil and there is no good apart from evil. … Evil is the origin of good. If there is no evil there can be no good. … Evil goes together with good. But this is neither evil nor good. … Good goes together with evil. But this is neither good nor evil.”

According to the ideas of nongood and nonevil and the nonduality of good and evil, the redemption of evil is possible. Based on this, moreover, the existence of evil comes to be positively affirmed as a source of good. The existence of evil enhances the quest for the good and elevates the good itself. In this sense, without evil there is no good. This prevents human beings who are caught between good and evil from having split personalities or falling into despair.

Tiantai’s theory that the Buddha includes evil in his nature or that the existence of evil is a source of good may give rise to an optimistic impression in which evil is treated lightly. There may be a danger of falling into decadence by affirming permission to do evil as one likes. In fact, later there were some who were severely criticized for understanding it in this way and putting this idea into practice. But the original intention was to try to find a possibility for salvation by looking directly at the reality of evil and hell, and grieving over it. This is neither to monistically affirm evil by seeing good and evil as having the same roots nor to deny the existence of evil.

To conclude, it is not the case that in this world there is only good and no evil. Rather, we can see the vitality of eternal life in the midst of the battle for good over evil. Through this theory of good and evil we can understand Tiantai’s general view of the world and human life. We can feel the vitality of life and find its meaning in a life woven of the warp and woof of happiness and sorrow, joy and suffering, good and evil. This is why Tiantai developed views of the absolute and of eternity.