Gregory was born in Cappadocia and educated at Athens, where he formed a lifelong friendship with Basil the Great. He wanted the contemplative life and was repeatedly pulled out of it — ordained against his inclination, made a bishop by his friend, and finally called to Constantinople when the city's churches had almost entirely gone over to Arianism.
He preached there in a small house chapel to a congregation that began as a handful. The five Theological Orations he delivered in that room are among the most influential sermons ever given: they are the reason the Church has the vocabulary it does for the Trinity, and they earned him the title 'the Theologian', shared in the East with only John the Evangelist. He resigned the see of Constantinople within two years and went home to write poetry.