Most religions conceive human beings as consisting of three parts: the physical body, the soul, and the spirit.
Hinduism calls the spirit, "Brahman," "Atman" or the absolute (metaphysical) self and the soul "jiva," or the miniature self. Buddhism calls the spirit the true heart, or Buddha-heart, and the soul the earthly heart, or the illusory heart. Taoism calls the spirit god's heart (which is absolute), and the soul the regular heart (which is relative and variable). Islam calls the spirit "Naf-matmainnah," which means "supernatural," and the soul "lawwama," which means "regular." In Christianity, Saint Paul recommends: "May your whole spirit, soul, and body be kept blameless at the coming of our lord Jesus Christ." The Vietnamese people call the spirit "linh hon" (sacred spirit) and the soul "tam hon" (emotional soul).
CaoDai believes in the law of justice, or karma, which means that any current situation is the result of past good or bad deeds; and therefore believes that the human soul evolves continuously according to this karmic law through many physical lives to become progressively purer, ultimately to unify with the Supreme Being (in Heaven).
Karmic law is also observed in other faiths:
Hinduism: “This body is called the Field, because a man sows seeds of action in it, and reaps their fruits.” (Bhagavad Gita)
Buddhism: “Even an evildoer sees happiness so long as his evil deed does not ripen; but when his evil deed ripens, then does the evildoer see evil.”
”Even a good man sees evil days so long as his good deed does not ripen; but when his good deed ripens, then does the good man sees good things.”
Taoism: “Those who do evil in the open light of day---men will punish them. Those who do evil in secret---God will punish them.”
Judaism: “Sow in righteousness, reap in mercy.” (Hos. 10:12)
"The merciful man doeth good to his own soul: but he that is cruel troubleth his own flesh... to him that soweth righteousness shall be a sure reward.”
Christianity: “Be not deceived; God is not mocked: for whatsoever a man soweth, that shall he also reap.”
Islam: “Whatever good you do for others, you send it before your own souls and find it with Allah who sees all you do.” (Koran 2:104)
Karmic law, or justice, is the divine law, the absolute law that is applied to all souls and that chains men to rebirth; or in other words, it requires that a man make payment for his transgressions: if not in the present life, then in another. Anyone who does anything--whether it be good or evil--receives its result, either in this life or in the next. No one escapes this law. Otherwise, there would be no justice. This law explains reincarnation as the spiritual evolution of all souls.
In accepting the Karma law and reincarnation, then life on this earth is just a place for the souls to experience (to reap) the deed that they have caused (sowed), in order to progress spiritually and to get closer to God in the spiritual journey to their divine origin. The Karma law reflects the absolute law of justice. In realizing this law, no one would not desire to cause to others what one does not desire others to do unto her/him.
CaoDai believes that with compassion, humanitarian service and meditation, one may pay back whatever kind of karmic debt that one had borrowed from previous life and become progressively detached from all secular distractions, therefore free from the effects of karmic law and avoid reincarnation, ultimately becoming one with the Supreme Being.