Most of what we have known hitherto concerning Archbishop Theodore is derived from Bede. Bede's information may be summarized briefly as follows. Theodore died, as archbishop of Canterbury, on 19 September 690, at the age of 88. He must accordingly have been born in 602. He was a native of Tarsus in Cilicia; he was well trained in secular and divine literature, both Greek and Latin; he was a monk after the eastern fashion who was living in Rome at the time the Englishman Wigheard arrived there to seek consecration as archbishop of Canterbury. But after Wigheard's sudden death in Rome from the plague (probably in 667), Pope Vitalian (657–72) resolved, after some negotiation, to consecrate Theodore to this archbishopric. Theodore was duly consecrated on 26 March 668. In company with Hadrian (on whom see below, ch. 3) and an Englishman then resident in Rome named Benedict Biscop, Theodore set off for England on 27 May 668; he arrived at the church of Canterbury a year later, on 27 May 669, to begin his archiepiscopacy. He will then have been 67 years old.

It will be seen that most of Bede's (meagre) information pertains to the latter part of Theodore's career, from his appointment by Pope Vitalian onwards, when he was already 66 years old. Concerning his earlier career Bede is silent. However, it is now possible, with the assistance of the present Canterbury biblical commentaries, to reconstruct something of the background and circumstances in which Theodore was educated before his election. Let us begin at Tarsus in Cilicia, where Theodore was born in 602.