Joseph had a notion to put Mary aside
delicately, for her trouble.
Trouble for her family and him.
But, he was a good man and wanted to keep things quiet ( as much as you can in a small town).
So quiet, he heard God speak and tell him to set aside his fears about Mary's trouble.
What seemed like trouble was really the son of God: Jesus,
conceived by the Holy Spirit,
which is inconceivable to some who can see trouble only.
Such things cannot happen, you see, inconceivable.
Joseph believed in a virgin birth and called his son, Jesus.
God is with us.
Some wonder how God did it, or if he did, and what does it matter, anyway.
Nothing new is conceived.
Others wonder and believe - like Joseph and Mary - and all manner of things inconceivable are conceived.