The kingdom's adoption of Theravada set a pattern for Burmese Buddhism that has held ever since, but it did not produce a single uniform religion, and Melford Spiro's study of Burmese practice is the standard account of what actually resulted. Spiro describes a system in which canonical Theravada teaching about karma, merit and release operates alongside a well organised cult of the nats, powerful spirits with their own shrines, mediums and festivals, and alongside a body of protective and apotropaic practice.
Practitioners do not experience these as competing religions. They address different problems: the canonical teaching concerns the long term fate of a person across lives, while the nats are approached about illness, business, travel and the immediate future. Spiro's framework has been criticised and refined since, and the atlas records it as an influential analysis rather than as the last word. What is clear is that the plain of temples represents one part of the religious life of the kingdom, the part that was monumental, royal and textual, and that the evidence for the rest is very much thinner because it was not built in brick and did not attract inscriptions. Any account of Bagan that reads the monuments as the whole of the religion is reading the surviving evidence as if it were a complete sample.