The ideas of the Greek philosophers were disseminated throughout the Roman Empire and remained influential until its fall in the fourth century C.E. By then Christianity was the official religion of the Roman Empire, and following the fall of Rome, the Christian church was essentially the sole surviving institution. Although many aspects of pagan philosophical thought were integrated into church teaching (e.g., Plato’s idea of the immortal soul), anything that did not fit with Christian theology was considered heretical. In Christendom, meaning most of Europe, this state of affairs remained largely unchanged until the dawn of the modern era. Thus questions of psychology were addressed through medieval Christianity.