Why the Roman empire became weak after it adopted Christianity?
It had been getting weak because of leaders who were decedent and cared more about their own lives than those of the people of the empire. They had everything, for a long time there was very little in the way of war and then the people on the outside of the empire, or barbarians, started to invade. Chrisitianity may have been slightly to blame because of a pacifist view, but as we know through most of western history, “Love thy neighbor” did not prevent lots of wars in Europe and other Christian countries. There were probably a lot of reasons for the decline, Christianity was probably not the cause, but as Emperors and leaders got a little less strong, they may have let Christians have more freedom of religion and not persecute them as much as previously. .
