Marcion was son of a bishop, born around 85AD. Through his study of the Hebrew scriptures, Marcion became convinced that the God of the Old Testament was incompatible with the Jesus of the New Testament. Around 144AD, he began to develop a theological system that incorporated two gods. There was a god of the Old Testament, the Demiurge, who created the material universe, but who was a legalistic and wrathful god. Another god, the one professed by Jesus, was altogether different. He was merciful and gracious, full of compassion and love. As a result of this, Marcion developed what could be considered an early canon of Scripture. Essentially, Marcion went to the New Testament with a knife and began removing everything he didn’t like. When he was finished, he was left with the Gospel of Luke (minus parts he didn’t like) and ten of Paul’s letters (also trimmed to fit his views). He had removed anything that favorable referenced the God of the Old Testament.
The Marcionite heresy continues to rear its ugly head. There is nothing new under the sun (Eccl 1:9), and old heresies just get rewarmed in a modern context. The mega-church pastor Andy Stanley recently preached that the Gospel needs to be “unhitched” from the Old Testament. He does this because he sees a fundamental difference between the “worldview and the values system depicted in the story of Ancient Israel” and the one depicted in the New Testament. Stanley is well-intentioned. His fear is that a mean, wrathful, and legalistic god of the Old Testament will scare away people from the merciful, gracious, and compassionate god of the New Testament. But his good intentions are just a re-hashing of Marcion’s errors.
What’s interesting about Marcion is that he has inadvertently been a great gift to the Church. What others intended for evil, God intended for good (Gen 50:20, Rom 8:28). In response to Marcion, the early Church had to clarify those areas where Marcion attempted to attack. The continuity between the Old and New Testaments was affirmed. The incarnation of Jesus Christ was explained. And the canon of the New Testament, which had been universally but unofficially received, was more formally acknowledged in order to refute Marcion’s canon. It is interesting to note that Marcion’s canon was clearly an attempt to cut away the pieces with which he disagreed. But for him to do that, there had to be an understood and received canon from which to cut. Marcion’s canon points to the fact that there already was an established, though somewhat unofficial, canon of the New Testament.
Out of the 2nd century response against Marcion came a prologue to Luke’s Gospel. This so called “Anti-Marcionite Prologue to the Gospel of Luke,” written around 160AD, helped to firmly establish the authorship of the anonymous Gospel. It says the physician Luke was the author of the Gospel and the book of Acts. It also points out that Luke wrote his Gospel to proclaim the truth of Jesus Christ to the Gentile world. The reason Marcion liked the Gospel of Luke is that Luke presented Jesus to a non-Jewish audience. Luke was careful to couch the narrative of Jesus in its proper Jewish context, but it was not emphasized like in Matthew or Mark.
Luke tells us in his opening why he wrote his Gospel. “Inasmuch as many have undertaken to compile a narrative…it seemed good to me also…to write an orderly account for you…that you may have certainty concerning the things you have been taught” (Luke 1:1-4). Luke was a physician and a historian. He took all the reliable accounts circulating at the time and he compiled them into an accurate and orderly account of Jesus’ life. As the fledgling Christian movement was growing, it was competing with a number of other religious and philosophical systems in the Greco-Roman world. Luke is presenting the best case that Christianity is not just for Jewish people, and why Christians are the true heirs of God’s Old Testament promises. For example, when Luke details the genealogy of Jesus, he traces it all the way back to Adam, whereas Matthew only goes back to Abraham. Luke also points out how Jesus commended Gentiles, like the widow of Zarephath and Naaman the Syrian (Luke 4:25-27), and the Roman centurion (Luke 7:1-10).
Luke makes some important and unique contributions. Luke provides for us a much more sweeping birth narrative of Jesus. Luke begins with the birth of John the Baptist and then moves to the much-loved nativity scene of Jesus. Luke also spends a great deal more time on the journey to Jerusalem than Matthew or Mark. What constitutes a mere chapter in them is extended to ten chapters (chs. 9-19). Included in this are some famous parables like the Good Samaritan (Luke 10:30-37) and the Prodigal Son (Luke 15:11-32).
Luke was a physician. And he presents Jesus as the compassionate and merciful healer. But he is also a Savior who denounces injustice and hates evil. Jesus is the one who not only heals the sick and ill, but he saves the lost from their sins (Luke 19:10). “The seeking love of God, as it appears [in Luke], is not the good-natured complacence that is being mistaken for it today, but a wonderful, paradoxical, saving will, that led the Son of God finally to the cross.”
 Machen and Cook, The New Testament, 208.