In "The Alchemist," how does Santiago's conversation with his father become true in his search for his Personal Legend?
Near the beginning of Santiago's quest for his Personal Legend, his father tries to dissuade his son from travel. He throws up impediments that might have changed Santiago's mind; claims such as travelers always "come in search of new things, but when they leave they are basically the same as when they arrived."
When that fails to change his son's mind, he appeals to tradition. "Amongst us," he says, "the only ones who travel are the shepherds." Santiago replies, "Well, then I'll be a shepherd."
His excuses exhausted, his father gives Santiago "three ancient Spanish gold coins." The biblical parallel should not be missed. In Matthew 25: 14-30, Jesus tells of three men who are given custody of money. The man who does not hoard his money is the one who is ultimately rewarded.
It is to Santiago's father's credit that he allows his boy to make his own decisions once he has proven strong enough to not be talked down from his choices. The boy knows his father is also somewhat envious of his youth and choices as
"he could see in his father's gaze a desire to be able, himself, to travel the world-- a desire that was still alive, despite his father's having had to bury it over dozen of years...".
Santiago has passed the first test of his quest toward realization of his Personal Legend. It becomes "true" when Santiago proves to have done well with his trust.