Ancient Iranian religion was strongly connected. Beginning in the early 10th-century BC, the ancient Iranian religion was gradually displaced by Zoroastrianism, which contains many essential aspects of its predecessor. The sources on ancient Iranian religion, though limited, consist of textual and material sources. The textual sources are both Iranian and non-Iranian. An important Iranian source is the Avesta, which are Zoroastrian sacred scriptures made in the Avestan. This is considered the principal source of knowledge on ancient Iranian religions. It is a collection of several texts that seems to have been over a large span of time by a variety of authors. These
The Religion of the Future stated that he considered the book, alongside Ronald Dworkin’s "Religion Without God", to be an example of “religious atheism,” that is, a “new attitude to God” that “presents a new horizon for Christianity.” While strongly criticizing the book from a theistic standpoint, Chapman allows that this new religious atheism may represent a “maturing of the infantile atheism offered by the scientific naturalism perspective: it looks at the world and finds moral truth, objective value, and goodness.” Reviewing "The Religion of the Future" in "Notre Dame Philosophical Reviews", Jeremy David Bendik-Keymer considered the book as the second part of the project