The toleration of Christianity decreed by the Edict of Toleration by (emperor) Galerius in 311 and by the Edict of Milan in 313 restored political stability. These edicts ended the Great Persecution of Christians unleashed by emperor Diocletian in 303. One of the aims was to restore peace. Christianity was widespread and the persecution led to widespread political unrest. The toleration ended the unrest and restored peace and political stability and gave the empire a greater sense of unity and cohesion. The toleration of Christianity did not contribute to growth in the empire. Imperial expansion had ended long before this and the priority had changed to defending the vast frontiers of the empire from continuous attacks from outside. The economy of the empire was in decline and this was not connected to religion.

Please remember, though, that Christianity was not the only religion that the Romans had to deal with. Centuries before Christianity was ever heard of the Romans were practicing their policy of tolerance while they were expanding. They absorbed the beliefs, gods and goddesses of conquered peoples or at least allowed them to continue to be worshiped. Many exotic cults were brought to Rome. This tolerance aided stability by creating a sense of oneness or unity among the various peoples of the empire.