Free speech, which implies the free expression of thoughts, was a challenge for pre-Christian rulers. It was no less troublesome to the guardians of Christianity, even more so as orthodoxy became established. To fend off a heretical threat to Christian doctrine church leaders introduced helpful measures, such as the Nicene Creed, promulgated in 325 AD. This profession of faith is still widely used in Christian liturgy today. As more books were written and copied and ever more widely disseminated, ideas perceived as subversive and heretical were spread beyond the control of the rulers. Consequently, censorship became more rigid, and punishment more severe.