Cao Dai teaches that there is one Supreme Being, addressed as Cao Dai, a name meaning high tower or highest power, and represented not by any human figure but by a single left eye set inside a triangle, the Divine Eye. The eye is the only permitted image of God, and it stands above the altar in every temple.
The founding claim is historical as much as theological. God is held to have sent revelation in earlier ages through Laozi, the Buddha, Confucius, Jesus and other teachers, and each time the message was narrowed by human transmission and by the limits of the culture receiving it. The twentieth century is understood as the Third Amnesty, in which God dispenses with intermediaries and teaches directly through spirit communication, so that the separated religions can be brought back together.
The result is a very wide roll of venerated figures. Alongside the founders of the great traditions, Cao Dai honours the sixteenth-century Vietnamese poet and prophet Nguyen Binh Khiem, the Chinese revolutionary Sun Yat-sen and the French novelist Victor Hugo, who appear together in a well known mural at Tay Ninh signing a covenant between God and humanity. The Tang poet Li Bai is regarded as a spiritual head of the religion.
Doctrine holds that souls reincarnate under karma and that the aim is release and return to God. Adherents keep at least six vegetarian days a month and frequently ten, and clergy keep a full vegetarian diet. Ordinary observance includes five precepts against killing, theft, luxury, intoxication and false speech, and prayer four times daily, at six in the morning, at noon, at six in the evening and at midnight.