On the feast of St. Luke, a parishioner wants to know what inspired him to write.
That question could be answered in many ways. One easy answer would be, as we believe that all scripture is writte and and protected by the Holy Spirit, we could just answer with that, "The Holy Spirit inspired Luke."
Another answer can be found in the opening lines of the Gospel. Luke's inspiration and information for his Gospel and Acts came from his close association with Paul and his companions as he explains in his introduction to the Gospel:
“Many have undertaken to draw up an account of the things that have been fulfilled among us, just as they were handed down to us by those who from the first were eye-witnesses and servants of the word. Therefore, since I myself have carefully investigated everything from the beginning, it seemed good also to me to write an orderly account for you, most excellent Theophilus, so that you may know the certainty of the things you have been taught.”
It seems that Luke had a desire to re-examine and re-investigate the stories and teachings of Jesus and write them down in an orderly manner. He also has a special connection with the women in Jesus' life. In Luke's gospel we hear the story of the Annunciation, Mary's visit to Elizabeth including the Magnificat, the Presentation, and the story of Jesus' disappearance in Jerusalem.
We have Luke to thank for parts of the Hail Mary: "Hail Mary full of grace" spoken at the Annunciation and "Blessed are you and blessed is the fruit of your womb Jesus" spoken by her cousin Elizabeth.
Forgiveness and God's mercy to sinners is also of first importance to Luke. Only in Luke do we hear the story of the Prodigal Son welcomed back by the overjoyed father. Only in Luke do we hear the story of the forgiven woman disrupting the feast by washing Jesus' feet with her tears. Throughout Luke's gospel, Jesus takes the side of the sinner who wants to return to God's mercy.
A final answer could be - "I am not 100% certain. You should ask him when you get to heaven." We hope this helps.