What is an apostle?

Discussion question for February 10, 2023.

The disciples, except Judas Iscariot, were considered apostles; and Paul made the argument that he was also an apostle.  How do you define the role of apostle?  What is the responsibility or duty of an apostle?  Who assigns that title, and in what way does that matter?  How much apostleship do you demonstrate with your life?  What more do you aspire to in this regard?  Some believe the role of apostle was closed after the disciples, so what difference does it make to the body of Christ if you believe that or disagree with it?