I am grateful to God for a series of conversations with Mary Boyce which changed my perspective and informed my opinion on the place of Zoroastrianism in our Scriptures. I reached her first by phone in late 2004 at the London University School of Oriental and African Studies on one of her last days there, before advancing age and debilitating illness began to take a severe toll. While researching for Noah's Other Son, which would be published in 2006, I developed a growing suspicion that there is more Zoroastrian influence in the Scriptures than is traditionally understood. Mary's revelations and suggestions came thick and fast, even as her light dimmed, and I soon had too much to include in that nearly finished book. As professor emerita still, through the winter of 2005 and into 2006, even shortly before her death that April, she believed we were onto something together.

As the world's leading English speaking authority on Zoroastrian texts, she had an anxiety that her own research had not sufficiently reported the evidence of interface between Zoroastrian Magi and Hebrew priests and scribes in Babylon during the Jewish Exile. Mary continued to mentor my understanding in ways that are touched on in the 2009 publication of Forensic Scriptures, and developed more fully in Three Testaments: Torah, Gospel and Quran. In particular, she gently recapitulated the still-smoldering controversies among scholars concerning the dates of Zoroaster, placing him either a thousand years or more before Christ (her position) or only a generation or two prior to the completion of the written text of the Torah as we have it (my position and that of her mentor and other respected colleagues). She modified her own long held position only enough to allow for the alternative, but equipped me to substantiate the position toward which we were working with reference to clearly identified "Z" passages in both the Bible and the Quran. Mary's particular contribution is noted in the Three Testaments text, though the designation of our shared perspective as "the Z factor" is mine, as is the identification of Zoroaster as "the axel of the Axial Age." In the subsequent Four Testaments we identify the Silk Route itself as the true “axis of the Axial Age,” but the designation of Zoroastrian words, phrases, verses and passages as Z material in the Hebrew, Christian and Islamic scriptures is extended to identifiable Vedic / Zoroastrian material in the Tao Te Ching, the Analects, the Dhammapada and the Bhagavad Gita. In both volumes of this compendium I am indebted for the contribution of expert scholars in the seven World Religions, but in this particular regard, nobody has contributed more than Mary Boyce.