It was one thing for Mary, who saw the angel Gabriel and was overshadowed by the Holy Spirit to have confidence that the growing child inside her belly was the Son of God.
It was quite another for Joseph, her betrothed, to take her word for it.
Contrary to the way we like to imagine “the olden days” intimate liaisons before marriage were just as common then as now. Betrothed couples were considered married in every way except physical consummation of the relationship. And not everyone waited for the final ceremony.
Read the rest here: Advent: [Nearly] Blind Trust