Though Mark's description of Jesus calling his first four disciples is brief, a look into the gospels of Luke and John proves that each of the four men had history with Jesus. By the time Jesus called them, they had come to their own convictions about who he was and were able to make an informed decision to follow him. To this day, the focus of Jesus' call to discipleship isn't based on the adequacy of those he calls, but on Christ's adequacy. The focus is on how he is able to work in us; we need only be available. Discipleship is a purpose-driven life, and we are often called upon to give some things up for the sake of following Christ.