Ifa is the divination system at the intellectual centre of Yoruba religion, and it is also a body of knowledge large enough to occupy a lifetime. It is associated with Orunmila, the orisha of wisdom, who is said to have witnessed the choosing of every person's destiny and therefore to know what each came into the world to do.
The mechanics are simple; the content is not. The diviner, a babalawo, manipulates sixteen sacred palm nuts or casts a divining chain, and records the result as one of 256 Odu, each a pair of columns of single and double marks. Each Odu indexes a large body of memorised verse, ese, telling of earlier clients who faced comparable situations, what they were told to offer, whether they complied and what followed. Several hundred ese per Odu is a commonly cited figure, and the corpus is not closed; it absorbs new material.
The diviner does not interpret freely. He recites until the client recognises their own case in one of the stories, and the prescription follows from the verse rather than from the diviner's opinion. This is why Ifa is often described as a jurisprudence as much as an oracle: precedent applied to a present situation.
Training is long, oral and demanding, and initiation into Ifa is distinct from initiation to an orisha. Women are initiated as iyanifa in some lineages, a practice widespread in parts of the diaspora and rejected in others where Ifa priesthood is held to be male. Practitioners genuinely disagree about this, and the disagreement is unresolved.
UNESCO proclaimed the Ifa divination system a Masterpiece of the Oral and Intangible Heritage of Humanity in 2005, citing both its value and the difficulty of transmitting it as the generation of senior babalawo ages.