Today, the Saint we meet, St Theodore the Studite, brings us to the middle of the medieval Byzantine period, in a somewhat turbulent period from the religious and political perspectives. Indeed it was his uncle (Plato, Abbot of the Monastery of Saccudium in Bithynia) who guided him towards monastic life, which he embraced at the age of 22. He was ordained a priest by Patriarch Tarasius.

Theodore distinguished himself within Church history as one of the great reformers of monastic life and as a defender of the veneration of sacred images, beside St Nicephorus, Patriarch of Constantinople, in the second phase of the iconoclasm. He also argues: abolishing veneration of the icon of Christ would mean repudiating his redeeming work, given that, in assuming human nature, the invisible eternal Word appeared in visible human flesh and in so doing sanctified the entire visible cosmos. Icons, sanctified by liturgical blessing and the prayers of the faithful, unite us with the Person of Christ, with his saints and, through them, with the heavenly Father.

However, the more influential was the new spirit the Founder impressed on coenobitic life. In his writings, he insists on the urgent need for a conscious return to the teaching of the Fathers, especially to St Basil, the first legislator of monastic life. Another of St Theodore's basic convictions was this: monks, differently from lay people, take on the commitment to observe the Christian duties with greater strictness and intensity.

— For Theodore the Studite an important virtue on a par with obedience and humility is “philergia”, that is, the love of work, in which he sees a criterion by which to judge the quality of personal devotion.