Reza Shah was not an atheist and could best be described as an agnostic. He was, for a while, fascinated by the teachings of Zoroaster, Iran's pre-Islamic prophet, but his fascination should be understood in the context of his old soldier's dream of restoring Iran to its ancient grandeur. Mohammad-Reza, on the other hand, was deeply religious, even to the point of rejecting all free will.

The Unknown Life of the Shah (1991)