The Edict of Milan of 313 finally legalized Christianity, with it gaining governmental privileges and a degree of official approval under Constantine, who granted privileges such as tax exemptions to Christian clergy. In the period of 313 to 391, both paganism and Christianity were legal religions, with their respective adherents vying for power in the Roman Empire. This period of transition is also known as the Constantinian shift. For the first two centuries of the Byzantine Empire, official policy towards paganism was cautious and tolerant. In 380, Theodosius I made Nicene Christianity the state church of the Roman Empire. Paganism was tolerated for another 12 years, until 392, when Theodosius passed legislation prohibiting all pagan worship. Pagan religions from this point were increasingly persecuted, a process which lasted throughout the 5th century. However, even with the closing of the Neoplatonic Academy by decree of Justinian I in 529, its philosophers were permitted to remain within the Empire without converting to Christianity,