In a key passage of the Syriac Book of the Laws of the Countries, Christians are described as residing among the Medes, Persians, Parthians, and Kushans. This statement has sometimes encouraged scholars to accept that Christianity had penetrated the Iranian plateau and central Asia by the early third century CE. But this testimony does not necessarily reflect the actual state of contemporary Christianity in such regions. Instead, it is based on a text that had been circulating in the eastern Mediterranean and upper Mesopotamia during the late second and early third centuries CE. This text, now lost, had ascribed the evangelization of such regions to the apostle Thomas.
