This thesis looks at the role of Peter and Judas in the four canonical gospels, seeking to answer the question of why two such dramatic examples of failure in discipleship became, from so early on, an established and central part of the gospel narrative. The first chapter discusses the literary context of the gospels, considering issues such as the oral medium, the gospel communities, and the genre of the gospels. The second chapter examines the historical Peter and Judas, discussing the evidence in the rest of the New Testament and elsewhere in Christian tradition, followed by a range of parallel disciple figures in ancient literature, from the followers and debate partners of Plato’s Socrates to the students of the neo-Platonic philosopher Plotinus, making the case that a literary archetype for a disciple exists and is made use of in all of these texts. The third, fourth, fifth and sixth chapters look at each of the gospels in turn, discussing the way in which Peter and Judas correspond to the literary archetype and the ways that this archetype interacts both with the actual events of Jesus’ career and arrest, and potentially ongoing or recent events in each evangelist’s own community.