What are the most prominent discrepancies in the gospels and how do you reconcile them?
What is most "prominent" may depend on the eye of the beholder. There are certainly many apparent discrepancies, some easy and some difficult. In some ways the most prominent apparent discrepancy consists in the differences between the Gospels in the presentation of the person of Christ himself (see previous answer). These differences can be quite dramatic for someone who has never noticed them before. But many believers have not found the differences to be much of a problem. They can see the compatibility. Jesus reveals the Father (as he does in the Gospel of John) precisely in his revealing himself as king of the Jews and Messiah (Matthew) and in revealing his compassion for the outcasts (Luke), a compassion that also reveals the heart of the Father (Luke 15). Jesus also reveals the Father by casting out demons and waging war on evil, as he does prominently in the Gospel of Mark.
When people have difficulty with these differences, the difficulty often comes from their assumptions about the meaning of historical events. The world around us often assumes that real "history" is "bare" events, and all interpretation of the meaning of events is a human addition. But this is a false, unbiblical view of the issue. God has a plan for all of history, and even the details of events are included in his comprehensive plan. There is meaning in his plan, even before the events actually take place. Through the Holy Spirit God empowered the Gospel writers to write in such a way as to show the meanings of events--meanings that were already there, not meanings "invented" by the writers. Each writer had his own human individuality, but God created and raised up the writer (Ps. 139) to be just who he was, and so the differences are what God wanted, not merely what each human writer wanted. Thus what we read in each Gospel is "the real thing," an aspect of God's own understanding of the events, written for our benefit. We are not getting a merely human "overlay" on bare events.
Some more specialized principles for dealing with discrepancies can be developed, once we have in place an understanding of the relation of history to God. Any account of an event, even an account given to us by God himself, is going to be selective rather than exhaustive. We will never have every detail and every angle of meaning about every detail. That means that not mentioning a detail is not an error. The Gospel writers are constantly selective, and when we lay two Gospels side by side, we regularly see details in one Gospel that are omitted in another. We can include here also the issue of details about geographical location and chronology. Often one of the Gospels describes an event without indicating explicitly when and where it took place. It is easy to assume that it must have taken place in the same location as the previous episode, and that it must have taken place at a time immediately after the episode that immediately precedes it on the page. But both of those moves are merely assumptions. They go beyond what the Gospel actually says. Consequently, we should not feel disappointed when we find that one or more episodes in one of the Gospels seems to be "out of chronological order" when compared with another Gospel. We should also acknowledge that, even when we take all four Gospels together, they do not give us enough explicit information to enable us to construct for certain a complete chronology. Of course the Gospels do indicate in some cases that one event follows another chronologically. But they do not always give us such information. Again, we can acknowledge that God is wiser than we are. God may on occasion have empowered a Gospel writer to place together material that is related thematically, rather than chronologically, so that we can better appreciate the thematic ties. God has given us what we need, not what we think we need (e.g., a single, completely chronological account).
Vern S. Poythress discusses why there are so many discrepancies within the Bible.
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