Simon the Magician was the big man on campus in Samaria. He performed his magic act regularly and commanded a sizeable audience every time. The crowd never suspected that Simon's power was not of God, until God's power arrived in the form of the evangelist Philip. Like Simon, many people can fool the world - and even themselves, but God's Spirit will reveal the truth in all of us sooner or later.
This teaching contrasts the false conversion of Simon with the true conversion of a pilgram from Ethiopia, taken from Acts 8.