I've got three partially finished notes sitting in my drafts, but none of them are coming together. So here's an easy one.
I can't count how many times I've heard people remark how crazy it is that when Jesus tells the disciples "follow me," (Matthew 4:19, Mark 1:17), they follow immediately. It's so crazy, they say, because the disciples have never seen him before. They don't even know who he is! All it takes are those two words, and off they go! Such faith! Wrong. They have seen him before. They know who he is. In fact, when Jesus comes to them on the shore of the lake, they are already his disciples. Remember that Matthew and Mark do not stand alone: they are part of a greater framework, a framework that includes Luke and, more importantly (for this discussion), John.
Let's look at the very beginning of John. Jesus is hanging out where John the Baptist is doing his baptisms and crying out in the wilderness and all that jazz--specifically, in Bethany (1:28), which is nowhere near Galilee. John sees Jesus and says his classic line, "Behold, the Lamb of God." Two of the Baptist's disciples hear this and probably figure that "Lamb of God" sounds way cooler than "The Baptist" (although, now that I think about it, "The Baptist" could be a good name for a professional wrestler). In any case, they follow Jesus and ask him where he's staying. In 1:40, we learn that one of those disciples (of the Baptist, at this point) was Andrew, the brother of Peter. The other unnamed disciple is most likely John (not the Baptist). Andrew gets Peter, there is an implication that John also got his brother, and the next day Phillip and Nathanael are called.
Here's the important bit: Andrew and (probably) John are pointed to Jesus by John the Baptist, who is not in prison at this point. Andrew brings Peter, there is an implication that John brings his brother, then come Phillip and Nathanael. So at least five, but probably six, disciples, before John is put in prison.
Now let's look at Matthew and Mark. Matthew 4:12 specifies the time of the following events: "Now when [Jesus] heard that John had been arrested, he withdrew into Galilee." Mark has the same qualifier in 1:14. A few verses later, Jesus meets Simon Andrew, James, and John on the shore of the Sea of Galilee and tells them to follow him. This is after John had been put in prison, meaning that it has to come after the events of John 1. That means that at this point, the disciples have already made an explicit commitment to follow Jesus. They are not following an unknown man, or even a rabbi that they've heard of but never seen or spoken to before. They are already his disciples, which is why they immediately drop what they're doing and follow him.
I may go more into the specifics of the likely chain of events later, but this note is already a little long. Remember: the gospels aren't true in the way that a really good story is true. They don't just tell us something true about human nature, or about God, or about the world. They tell us a true story--a story which actually happened. We cannot afford to shrug off apparent inconsistencies as "not important." We must be ready and prepared to demonstrate the harmony of the gospels--the harmony not only of ideas, but of actual events.
