In the Bible, the book of The Acts of the Apostles tells the story of the first days of the church. It's the companion book to the Gospel of Luke and they're generally considered to have been authored by the same person (or persons), the gospel telling the story of Jesus, Acts, the story of the apostles.
Well, kind of. It rather depends on how you define apostle. Some people hear apostle and disciple as being interchangeable depending on what's happening rather than who's doing it. The word "apostle" means a messenger or missionary, someone sent out. "Disciple," on the other hand, means a student, a learner or follower of a teacher. There's certainly plenty of both, and not just in the Bible.
But, for some people, there were only twelve apostles, the original ones chosen and commissioned by Jesus. Or thirteen, depending on how you count.
The Book of Acts - lets just call it that for now, to focus on the action rather than the doers - begins with the transitional story of Jesus ascending to heaven. Then, one might expect, the story of Pentecost is next, the coming of the Holy Spirit that Jesus promised. But, according to Luke, something else has to happen first.
The disciples were gathered together. And by disciples - that is, the followers of Jesus - Luke says there's the eleven chosen by Jesus (Judas was now dead) plus others, including women, numbering about 120. Peter stands up and says that there needs to be a replacement for Judas. He says that scripture had to be fulfilled in Judas, but he might just as easily have said that Jesus picked twelve, so there needs to be twelve, a full team. They need a replacement. Two names are proposed and they pick Matthias … who is never mentioned by name again.
We don't even know who Matthias was. The only criteria Peter gave was that the person had to have been a disciple "from the baptism of John until the day when he was taken from us" and that they "become a witness with us to the resurrection" (Acts 1:22). Then they pray for God to show them which of the two is chosen and it's Matthias. The story moves on to the promised coming of the Holy Spirit at Pentecost.
By Peter's criteria, then, Paul - the one known as "apostle to the Gentiles" - would not be an apostle. He wasn't there. No one since would be an apostle, either. But Matthias, even though he was there, apparently, still was not chosen by Jesus. Judas was chosen by Jesus, but Judas seems to have made his own choice not to be a disciple. Or an apostle. Or so we think. There's some thought now that Judas was the truest of disciples who did what no other follower could, or would, do.
But this is why I think Matthias is so special. He's not a nobody, he's officially the first person who chose to accept the call to be an apostle who was not called by Jesus in person. There have been so many more, those who chose to be disciples and became apostles as well.
That's why I think we have to go with the meaning of the word, not the exclusive club of those chosen personally (no offense, original eleven). Because, like everyone, from the first called to the most recent chosen, we can be both disciple and apostle. Jesus calls us to be both, to be learners and teachers, followers and leaders, each in our own way. Sometimes we experience that as a personal call from Jesus, sometimes we recognize it in a request from a friend, a stranger's need or community's desire.
Mathias isn't a nobody. He's you and me.