Luke and Divine Inspiration

My church started a new Bible study last night.  We're going through Luke: Gospel of Reassurance, with Michael Card.  The main theme last night was who Luke was and how that influenced his writing of his Gospel.  Luke was a Gentile, and that influenced him to highlight the Gospel going to the Gentiles.  He was a physician, and Michael Card said that the physicians he knows are men of prayer, and that could be why Luke's Gospel has a lot of emphasis on prayer.  Michael Card speculated that Luke was a slave, since many physicians in the ancient world (such as Emperor Augustus' physician) were slaves, plus Luke was a slave name.  Could Luke's status as a slave (assuming that Michael Card is correct on this) explain the sensitivity of his Gospel to the poor and the marginalized?

We read Luke's introduction in Luke 1, where he said that he was gathering information from eyewitnesses and was writing so that Theophilus might know with certainty about that in which he had been instructed.  Michael Card said (if I remember correctly) that the stories in Luke about Jesus' birth and childhood may have been due to Luke's consultation of Mary, the mother of Jesus.  The pastor was asking if people in the ancient world would value Luke's references to the testimony of eyewitnesses rather than the testimony of eyewitnesses themselves, of the sort that we see in Matthew's Gospel.  (My pastor believes that the apostle Matthew, who was with Jesus as a disciple, wrote the Gospel of Matthew.)  People in the group were acknowledging the difficulty of writing a history from the testimonies of eyewitnesses, since different people have different accounts.  But the people in the group seemed to believe that Luke wrote an accurate life of Jesus, for physicians pay attention to details, and Luke, according to II Timothy 4:9-11, stuck with Paul when others had forsaken him, showing that Luke was a man of character whose Gospel can be trusted. 

Our workbook asked: "How do you think the Holy Spirit was involved in the process of Luke's researching and writing his account, which eventually came to be included in Scripture?"  That is an excellent question, even if you are a believer who does not accept all of Michael Card's ideas about the authorship and composition of the Gospel of Luke, preferring other scholarly scenarios instead.  Where does Luke end, and where does God begin?  I one time wrote a paper for a Jewish theology class, in which I was seeking to explain my view as to how the Bible was divine revelation.  I wrote that I believed that God inspired human authors, while preserving their own personalities.  My professor was puzzled by that model of revelation.  He wondered if I was saying that the Bible contained God's words, or human authors' words, or somehow both.

I don't have a fully satisfactory answer to my professor's question, but I wonder: maybe God could communicate truth while still preserving the personality of the human authors.  Who Luke was as a person may have influenced him to highlight certain aspects of God's truth----the Gospel going to the Gentiles, social justice, prayer, etc.----but he was still communicating aspects of God's truth.  By reading Luke, perhaps we're getting a window into the mind of Luke, but also (on some level) the mind of God.