The Purpose of Luke-Acts
It is easier to describe Luke's purposes rather than a singular purpose. Although there are a number of possibilities the most obvious fall into the areas of history, the universal nature of the gospel, and to encourage Theophilus.
It is history in that it narrates the birth and growth of the early church from Jerusalem to Rome, spanning a period of thirty years. Luke makes it clear in the Prologue to his gospel (1:1-4)that he plans on writing an "orderly account" of all the things that had taken place among Jesus' followers. Acts seems to carry with it this same purpose. Acts is an account of Christ manifested in the world through His Church. The gospel of Luke recorded what Jesus "began to do and teach" (Acts 1:1). The word "began" shows that the first book was a beginning, while this second volume, Acts, records the next phase of the movement of Christianity. Luke can be broken into six sections where he records the history of this aggressive movement. Each of these sections ends with a general statement and a comment upon the process. First, is Acts 1:1 - 6:3 which ends with "So the word of God spread. The number of disciples in Jerusalem increased rapidly, and a large number of priests became obedient to the faith" (6:7). The second section deals with Hellenistic evangelism and begins with 6:8 and ends at 9:31 with an obvious reference to the Great Commission, "Then the church throughout Judea, Galilee and Samaria enjoyed a time of peace" (9:31). The third section runs from 9:32-12:24. It begins with Peter's evangelistic trip which opened up the gospel for the Gentile world and ends with the statement, "but the word of God continued to increase and spread" (12:24). The fourth section of Luke's history is found from 12:25-16:5 and covers the great movement of Gentile evangelism. This section concludes with, "so the churches were strengthened in the faith and grew daily in numbers" (16:5). The fifth section traces Paul's progress to Ephesus (16:6-19:20) and ends with, "in this way the word of the Lord spread widely and grew in power" (19:20). The last section runs from 19:21 through the end of the book and ends with this statement about Paul, "boldly and without hindrance he preached the kingdom of God and taught about the Lord Jesus Christ" (28:31).
In all of these sections Luke records the history of the early church. He traces its growth, its disappointments, its heros and it villains.
Another purpose for Luke's writing Acts is to continue his focus on the universal nature of the gospel that began in his first volume. The same inclusive language is used throughout the book of Acts. The commission is repeated (1:8) and includes all ethnic groups. Peter's Pentecost sermon includes a promise, not only for the nation of Israel, but also for those who are "far off" (2:39). In Acts 10 the gospel is introduced to the Gentile community formally. In that chapter Cornelius the centurion is visited by an angel (vss. 3-6), Peter is sent to him and preaches the Gospel (vss. 9-43), which results in Cornelius and his household all receiving the Holy Spirit and then being baptized with water (vss. 44-48). In this account Cornelius is held in high esteem by the Jewish community, by God, and by Peter the Apostle. Peter is instructed by the angel to recognize Gentiles as "clean" (vs. 15), and communicates this new revelation to Cornelius and his companions (vs. 28). This change in policy is questioned by the Jewish Christians in chapter 11, where Peter's defense is accepted and those who opposed this new venture are left proclaiming, "so then, God has granted even the Gentiles repentance unto life" (vs. 18).
While Luke emphasizes, in both Luke and Acts, that the roots of Christianity are found in Judaism, God intended from the beginning to gain for Himself a people from all the nations of the earth. This is vividly displayed in the ministry of Paul. Paul was the apostle to the Gentiles, but he usually went first to the Jewish synagogue when he arrived in a town. All of the disciples were Jewish but the Gospel would spread through them to the Gentiles.
From a comparison of the prologues, a third and practical purpose emerges for Luke-Acts: Theophilus needed to be encouraged and challenged in his faith. While this book was obviously meant for a larger audience than just one man, it was meant to fulfill this purpose in both Theophilus' and other's lives.
Other possible purposes that have been suggested would include: 1) to provide an apologetic for Paul's apostleship, and 2)to provide an apologetic for Christianity, in order to establish its character as nonthreatening to the Roman Empire.