Gospel originally meant the Christian message, but in the 2nd century it came to be used also for the books in which the message was set out; in this sense a gospel can be defined as a loose-knit, episodic narrative of the words and deeds of Jesus of Nazareth, culminating in his trial and death and concluding with various reports of his post-resurrection appearances. The four canonical gospels of Matthew, Mark, Luke and John share the same basic outline: Jesus begins his public ministry in conjunction with that of John the Baptist, calls disciples, teaches and heals and confronts the Pharisees, dies on the cross, and is raised from the dead. Each has its own distinctive understanding of Jesus and his divine role: Mark never calls him "God", Luke follows Mark's plot more faithfully than does Matthew but expands on him while eliminating some passages entirely, and John, the most overtly theological, is the first to make Christological judgements outside the context of the narrative of Jesus's life. They contain details which are irreconcilable, and attempts to harmonize them would be disruptive to their distinct theological messages.The four canonical gospels were probably written between AD 66 and 110. All four were anonymous (the modern names were added in the 2nd century), almost certainly none were by eyewitnesses, and all are the end-products of long oral and written transmission. Mark was the first to be written, using a variety of sources; the authors of Matthew and Luke, acting independently, used Mark for their narrative of Jesus's career, supplementing it with the collection of sayings called the Q document and additional material unique to each; and there is a near-consensus that John had its origins as a "signs" source (or gospel) that circulated within a Johannine community. The contradictions and discrepancies between the first three and John make it impossible to accept both traditions as equally reliable. Modern scholars are cautious of relying on the gospels uncritically, but nevertheless they do provide a good idea of the public career of Jesus, and critical study can attempt to distinguish the original ideas of Jesus from those of the later authors.Many non-canonical gospels were also written, all later than the four canonical gospels, and like them advocating the particular theological views of their various authors. Important examples include the Gospel of Thomas, the Gospel of Peter, the Gospel of Judas, the Gospel of Mary, infancy gospels such as the Gospel of James (the first to introduce the perpetual virginity of Mary), and gospel harmonies such as the Diatessaron.