Family and childhood
Theodore was born in
Constantinople in 759.
 He was the oldest son of
Photeinos, an important financial official in the
 and Theoktiste, herself the offspring of a distinguished Constantinopolitan family.
 The brother of Theoktiste, Theodore's uncle
Platon, was himself an important official in the imperial financial administration.
 The family therefore controlled a significant portion, if not all, of the imperial financial administration during the reign of
Constantine V (r. 741–775).
 Theodore had two younger brothers (
Archbishop of Thessalonica, and Euthymios) and one sister, whose name we do not know.
It has often been assumed that Theodore's family belonged to the
iconodule party during the first period of
Byzantine Iconoclasm. There is however no evidence to support this, and their high position in the imperial bureaucracy of the time renders any openly iconodule position highly unlikely. Furthermore, when Platon left his office and entered the priesthood in 759, he was ordained by an abbot who, if he was not actively iconoclastic himself, at the very least offered no resistance to the iconoclastic policies of Constantine V. The family as a whole was most likely indifferent to the question of icons during this period.
According to the later hagiographical literature, Theodore received an education befitting his family's station, and from the age of seven was instructed by a private tutor, eventually concentrating in particular on theology. It is however not clear that these opportunities were available to even the most well-placed Byzantine families of the eighth century, and it is possible that Theodore was at least partially an autodidact.
Early monastic career
Following the death of Emperor
Leo IV (r. 775–780) in 780, Theodore's uncle Platon, who had lived as a monk in the Symbola Monastery in
Bithynia since 759, visited Constantinople, and persuaded the entire family of his sister, Theoktiste, to likewise take monastic vows. Theodore, together with his father, brothers, sailed back to Bithynia with Platon in 781, where they set about transforming the family estate into a religious establishment, which became known as the Sakkudion Monastery. Platon became abbot of the new foundation, and Theodore was his "right hand." The two sought to order the monastery according to the writings of
Basil of Caesarea.
During the period of the regency of
Eirene, Abbot Platon emerged as a supporter of the
Patriarch Tarasios, and was a member of Tarasios's iconodule party at the
Second Council of Nicaea, where the veneration of icons was declared orthodox. Shortly thereafter Tarasios himself ordained Theodore as a priest. In 794, Theodore became abbot of the Sakkudion Monastery, while Platon withdrew from the daily operation of the monastery and dedicated himself to silence.
Conflict with Constantine VI
Also in 794, Emperor
Constantine VI (r. 776–797) decided to separate from his first wife,
Maria of Amnia, and to marry Maria's kubikularia (
Theodote, a cousin of Theodore the Studite.
 Although the Patriarch may initially have resisted this development, as a divorce without proof of adultery on the part of the wife could be construed as illegal, he ultimately gave way. The marriage of Constantine and Theodote was celebrated in 795, although not by the patriarch, as was normal, but by a certain Joseph, a priest of Hagia Sophia.
A somewhat obscure chain of events followed (the so-called "Moechian controversy," from the Greek moichos, "adulterer"), in which Theodore initiated a protest against the marriage from the Sakkudion Monastery, and appears to have demanded the excommunication, not only of the priest Joseph, but also of all who had received communion from him, which, as Joseph was a priest of the imperial church, included implicitly the emperor and his court.
 This demand had no official weight, however, and Constantine appears to have attempted to make peace with Theodore and Platon (who, on account of his marriage, were now his relatives), inviting them to visit him during a sojourn at the imperial baths of Prusa in Bithynia. In the event neither appeared.
As a result, imperial troops were sent to the Sakkudion Monastery, and the community was dispersed. Theodore was flogged, and, together with ten other monks, banished to Thessaloniki, while Platon was imprisoned in Constantinople.
 The monks arrived in Thessaloniki in March 797, but did not remain for long; in August of the same year Constantine VI was blinded and overthrown, and his mother Irene, the new empress, lifted the exile.
Abbot of the Studites
The Stoudios Monastery as depicted in an 11th-century manuscript.
Following the accession of Irene, the priest Joseph was stripped of his office, and Theodoros was received in the imperial palace.
 The monks then returned to the Sakkudion Monastery, but were forced back to the capital in either 797 or 798 on account of an Arab raid on Bithynia. At this time, Irene offered Theodore the leadership of the ancient
Stoudios Monastery in Constantinople, which he accepted.
 Theodore then set about building various workshops within the monastery to guarantee
autarky, constructing a library and a
scriptorium, and restoring and decorating the church. He also composed a series of poems on the duties of the various members of the community, which were likely inscribed and displayed within the monastery.
 He furthermore composed a rule for the governance of the monastery,
 and made the Studios community the center of an extensive congregation of dependent monasteries, including the Sakkudion. He maintained contact with these other monasteries above all through his prodigious literary output (letters as well as
catechisms), which reached a quantitative peak at this time, and developed a system of messengers that was so elaborate as to resemble a private postal service.
To this period may also date the so-called iconophile epigrams,
acrostics composed by Theodore that replaced the "iconoclastic epigrams" which were previously exhibited on the
Chalke gate of the
Great Palace. It has been suggested that these were commissioned by Irene, as another sign of her good favor toward Theodore, although a commission under
Michael I Rangabe (r. 811–813) is also possible; in any case, they were removed in 815 by
Leo V the Armenian (r. 813–820) and replaced by new "iconoclastic" verses.
In 806, the Patriarch Tarasios died, and Emperor
Nikephoros I (r. 802–811) set about seeking his replacement.
 It appears likely that Platon at this time put forth Theodore's name,
Nikephoros, a layman who held the rank of
asekretis in the imperial bureaucracy, was chosen instead.
 The selection of Nikephoros gave rise to an immediate protest on the part of the Studites, and in particular Theodore and Platon, who objected to the elevation of a layman to the patriarchal throne. Theodore and Platon were jailed for 24 days before the Emperor Nikephoros allowed them to return to their congregations.
Conflict with Nikephoros
Emperor Nikephoros soon requested that his new patriarch rehabilitate the priest Joseph, who had officiated at the wedding of Constantine and Theodote, possibly because Joseph had aided in the peaceful resolution of the revolt of
Bardanes Tourkos. In 806, the Patriarch Nikephoros convened a
synod to address the case, at which Theodore was present. The Synod decided to readmit Joseph to the priesthood, a decision to which Theodore did not at the time object.
Therefore, relations between the Studite Abbot and the Patriarch appear to have been initially untroubled, an impression which is reinforced by the choice (806/807) of Theodore's brother, Joseph, as Archbishop of Thesaloniki.
 However, soon after this ordination, perhaps in 808, Theodore began to express his unwillingness to associate with the rehabilitated priest Joseph, or for that matter with anyone else who knowingly associated with him, as he held the rehabilitation for uncanonical. As in the first dispute over the priest Joseph, the extension of this refusal beyond Joseph to those who associated with him included implicitly the patriarch and the emperor himself.
Early in 808, Theodoros offered in a series of letters to explain his position to the emperor, and furthermore to perform the customary
proskynesis at his feet, which offer Nikephoros declined, instead setting off for the summer military campaign.
 In the winter of the same year, Theodore's brother Joseph visited him in Constantinople, but refused to attend the Christmas mass in Hagia Sophia, at which the emperor, the patriarch, and the priest Joseph would have been present. As a result, he was stripped of his archbishopric.
 At around the same time a small military division was dispatched to the Stoudios Monastery to arrest Theodore, Joseph, and Platon.
 A synod was then held in January of 809, at which Theodore and his followers were anathematized as schismatic.
 Theodore, Joseph, and Platon, were thereafter banished to the
Princes' Islands: Theodore to
Chalke, Joseph to
Prote, and Platon to
Theodore maintained an extensive literary activity in exile, writing numerous letters to correspondents including his brother, various Studite monks, influential family members, and even
Pope Leo III. He also continued to compose catechisms for the Studite congregation, as well as a number of poems.
Rehabilitation under Michael I
In 811, the new emperor
Michael I Rangabe called the Studites back from exile. The priest Joseph was once more defrocked, and Theodore was, at least superficially, reconciled with the Patriarch Nikephoros.
There are, however, indications that a certain rivalry between the Studite Abbot and the Patriarch persisted. In 812, Michael I resolved to persecute certain heretics in
Lycaonia, namely the
Paulicians and the "Athinganoi" (sometimes identified with the
Roma). Theodore and Nikephoros were called before the emperor to debate the legality of punishing heresy by death, Theodore arguing against and Nikephoros for. Theodore is said to have won the day.
The second affair concerned a peace treaty proposed by
Krum of Bulgaria (r. 803–814), also in 812, according to which the Byzantine and Bulgarian states should exchange refugees. It is likely that Krum sought the return of certain Bulgarians who had betrayed him to the Byzantines. In this instance Theodore argued against the exchange, as it would require that Christians be cast to barbarians, while Nikephoros urged the emperor to accept the treaty. Once more Theodore's opinion prevailed, although this time with serious consequences; Krum attacked and took
Mesembria in November of the same year.
 Michael led a military campaign against the Bulgarians in 813, which ended in defeat, and as a result he abdicated in July and
Leo V was crowned emperor.
On April 4, 814, Theodore's uncle Platon died in the Stoudios Monastery after a long illness. Theodore composed a long funeral oration, the Laudatio Platonis, which remains one of the most important sources for the history of the family.
At the very beginning of his reign, Leo V faced a new Bulgarian offensive that reached the walls of Constantinople and ravaged large sections of
Thrace. This came to an end with the death of Krum on April 13, 814, and the internal power struggles that followed.
 However, as the previous 30 years since the approval of icon-veneration at the Synod of 787 had represented for the Byzantines a string of military catastrophes, Leo resolved to reach back to the policies of the more successful Isaurian dynasty. He renamed his son Constantine, thus drawing a parallel to
Leo III (r. 717–741) and
Constantine V, and beginning in 814 began to discuss with various clerics and senators the possibility of reviving the iconoclastic policy of the Isaurians. This movement met with strong opposition from the Patriarch Nikephoros, who himself gathered a group of bishops and abbots about him and swore them to uphold the veneration of images. The dispute came to a head in a debate between the two parties before the emperor in the Great Palace on Christmas 814, at which Theodore and his brother Joseph were present, and took the side of the iconophiles.
Leo held fast by his plan to revive iconoclasm, and in March 815 the Patrarch Nikephoros was stripped of his office and exiled to Bithynia. At this point Theodore remained in Constantinople, and assumed a leading role in the iconodule opposition. On March 25, Palm Sunday, he commanded his monks to process through the monastery's vineyard, holding up icons so that they could be seen over the walls by the neighbors. This provocation elicited only a rebuke from the emperor.
A new patriarch,
Theodotos, was selected, and in April a synod was convened in Hagia Sophia, at which iconoclasm was re-introduced as dogma. Theodore composed a series of letters in which he called on "all, near and far," to revolt against the decision of the synod. Not long thereafter he was exiled by imperial command to a Metopa, a fortress on the eastern shore of
Lake Apollonia in Bithynia.
 Shortly thereafter Leo had Theodore's poems removed from the Chalke Gate and replaced by a new set of "iconoclastic" epigrams.
While Theodore was in exile, the leadership of the Studite congregation was assumed by the Abbot Leontios, who for a time adopted the iconoclast position and won over many individuals monks to his party.
 He was, however, eventually won back to the iconodule party.
 The Studite situation mirrored a general trend, with a number of bishops and abbots at first willing to reach a compromise with the iconoclasts,
 but then in the years between 816 and 819 renouncing the iconoclast position, a movement that was perhaps motivated by the martyrdom of the Studite monk Thaddaios.
 It was during this upswell in icondule sentiment that Theodore began to compose his own polemic against the iconoclasts, the Refutatio, concentrating in particular on refuting the arguments and criticizing the literary merits of the new iconoclastic epigrams on the Chalke.
Theodore exercised a wide influence during the first year of his exile, primarily through a massive letter-writing campaign. Accordingly, he was transferred in 816 to Boneta, a fortress in the more remote
Anatolic theme, whence he nevertheless remained abreast of developments in the capital and maintained a regular correspondence. This continued activity led to an imperial order that Theodore be whipped, which his captors however refused to carry out.
 In 817, Theodore wrote two letters to
Pope Paschal I, which were co-signed by several fellow iconophile abbots, in the first requesting that he summon an anti-iconoclastic Synod; letters to the Patriarchs of
Jerusalem, among other "foreign" clerics, followed.
 As a result, the emperor ordered at least once more that Theodore be flogged, and the command was this time carried out, with the result that Theodore became quite ill.
 After his recovery Theodore was moved to
Smyrna. Early in 821, however, Leo V fell victim to a grisly murder at the altar of the Church of St. Stephen in the
imperial palace; Theodore was released from exile shortly thereafter.
Following his release, Theodore made his way back to Constantinople, travelling through north-western Anatolia and meeting with numerous monks and abbots on the way. At the time he appears to have believed that the new emperor,
Michael II (r. 820–829), would adopt a pro-icons policy, and he expressed this hope in two letters to Michael.
 An imperial audience was arranged for a group of iconodule clerics, including Theodore, at which however Michael expressed his attention to "leave the church as he had found it." The abbots were to be allowed to venerate images if they so wished, as long as they remained outside of Constantinople. Theodore returned to Anatolia, in what seems to have been a sort of self-imposed exile.
Theodore's activities in his final years are somewhat difficult to trace. He continued to write numerous letters supporting the use of icons, and appears to have remained an important leader of the opposition to imperial iconoclasm.
 He was present at a meeting of "more than a hundred" iconodule clerics in 823 or 824, which ended in an argument between the Studites and the host, one Ioannikos, which may have represented a power struggle within the movement.
 Theodore also spoke against the second marriage of Michael II to the nun Euphrosyne, a daughter of Constantine VI, although in a very moderate fashion, and with none of the passion or effect of the Moechian controversy.
Theodore's years of exile, regular fasting, and exceptional exertions had taken their toll, and in 826 he became quite ill.
 In this year, he dictated his Testament, a form of spiritual guidance for the future abbots of the Stoudios monastery, to his disciple Naukratios.
 He died on the 11 of November of that same year, while celebrating mass, apparently in the monastery of Hagios Tryphon on Cape Akritas in Bithynia. Eighteen years later, his remains, along with those of his brother Joseph, were brought back to the Stoudios Monastery, where they were interred beside the grave of their uncle Platon.