Maximus the Confessor

He was born in Constantinople, was well educated, and spent some time in government service before becoming a monk. He vigorously opposed the doctrine of monothelitism, to the point of breaking communion with both the Byzantine Emperor and the Patriarch of Constantinople. Eventually, the emperor had his tongue and right hand cut off so that he could no longer speak or write, and sent him into exile.

Nevertheless, Maximus was ultimately exonerated and canonized as a saint. He argued for dythelitism, the notion that Jesus Christ possessed two wills, rather than the one will posited by monothelitism. He left many writings that are still widely read today; some are doctrinal, but many more describe the contemplative life and offer spiritual advice. His theological work was later continued by Saint Simeon the New Theologian and by Saint Gregory Palamas.