Catholic Christianity , as opposed to Arianism and other ideologies deemed heretical , was declared to be the state religion of the Roman Empire on 27 February 380 by the decree `` De Fide Catolica '' of Emperor Theodosius I. Han dynasty Confucianism .
Catholic Christianity , as opposed to Arianism and other heretical and schismatic groups , was declared to be the state religion of the Roman Empire on February 27 380 by the decree `` De Fide Catolica '' of Emperor Theodosius I. Han Dynasty Confucianism and Sui Dynasty Buddhism .