Yahya ibn Adi was, in his day, among the foremost philosophers in Medieval Baghdad. He was particularly renowned in Aristotelian circles. He wrote in Arabic.
Nevertheless, he was a Christian. At this period, which was the intellectual height of Islamic civilization, having a leading thinker in the heart of the Islamic world who was not Muslim was in no way threatening to the rulers. Ibn Adi engaged in an extended philosophical defense of the Trinity, and engaged both prominent Muslim and Jewish thinkers on philosophical and theological topics. No one thought to cut off his head. Rather, he both studied under and was allowed to teach Muslims as well as Christians.
Medieval Baghdad wasn't perfect, but it was better than Modern Baghdad. Oh, it didn't have electricity or access to the many scientific advances we have today. Yet it was a better place to live, to think, and to be a part of the community.