How may we reconcile the Blessed Virgin Mary's maturity with her age?

Question

The Catholic Encyclopedia says:

[Based on] the age at which Hebrew maidens became marriageable, it is possible that Mary gave birth to her Son when she was about thirteen or fourteen years of age. No historical document tells us how old she actually was at the time of the Nativity.

How may we reconcile the Blessed Virgin Mary's possibly young age with the evident maturity of her speech in scripture? For example, consider The Canticle of Mary, Luke 1:46:

And Mary said:
“My soul proclaims the greatness of the Lord;
my spirit rejoices in God my savior.
For he has looked upon his handmaid’s lowliness;
behold, from now on will all ages call me blessed.
The Mighty One has done great things for me,
and holy is his name.
His mercy is from age to age
to those who fear him.
He has shown might with his arm,
dispersed the arrogant of mind and heart.
He has thrown down the rulers from their thrones
but lifted up the lowly.
The hungry he has filled with good things;
the rich he has sent away empty.
He has helped Israel his servant,
remembering his mercy,
according to his promise to our fathers,
to Abraham and to his descendants forever.”

Answer 1

The Magnificat or the Canticle of Mary (Luke 1:46-56) mirrors Hannah's prayer found in 1 Samuel 2:1-10 so closely that one would have to think that Mary found her words in through reflecting on scripture.

And Hannah prayed:	And Mary said:
My heart exults in the LORD, my horn is exalted by my God.	“My soul proclaims the greatness of the Lord; my spirit rejoices in God my savior For he has looked upon his handmaid’s lowliness; behold, from now on will all ages call me blessed. The Mighty One has done great things for me, and holy is his name His mercy is from age to age to those who fear him.
I have swallowed up my enemies; I rejoice in your victory. There is no Holy One like the LORD; there is no Rock like our God. Speak boastfully no longer, Do not let arrogance issue from your mouths. For an all-knowing God is the LORD, a God who weighs actions.
“The bows of the mighty are broken, while the tottering gird on strength	He has shown might with his arm, dispersed the arrogant of mind and heart.
The well-fed hire themselves out for bread,	He has thrown down the rulers from their thrones but lifted up the lowly
while the hungry no longer have to toil.	The hungry he has filled with good things; the rich he has sent away empty
The barren wife bears seven sons, while the mother of many languishes. “The LORD puts to death and gives life, casts down to Sheol and brings up again. The LORD makes poor and makes rich, humbles, and also exalts. He raises the needy from the dust; from the ash heap lifts up the poor, To seat them with nobles and make a glorious throne their heritage. “For the pillars of the earth are the LORD’s, and he has set the world upon them.
He guards the footsteps of his faithful ones,	He has helped Israel his servant, remembering his mercy,
but the wicked shall perish in the darkness; for not by strength does one prevail. The LORD’s foes shall be shattered; the Most High in heaven thunders; the LORD judges the ends of the earth. May he give strength to his king, and exalt the horn of his anointed!”
	according to his promise to our fathers, to Abraham and to his descendants forever.”

That scripture, which would have been burned in to her Immaculate Heart, by means of a singular grace would have certainly been with her at a young age when she would be betrothed.

Furthermore, one tradition (not Sacred Tradition), which is mostly forgotten by popular imagery but found in the Catholic Encyclopedia article you linked to, says that Mary was a consecrated virgin raised in the temple. Her parents Anne and Joachim prayed for her and when they got her, gave her up to the temple where she would have been able to absorb scripture like Anna (Luke 2:36-38). There she would have certainly known all about Hannah and Samuel, certainly enough to put Hannah's prayer into her own words.

Answer 2

Luke, the author of the gospel that bears his name and also of Acts, was an exceptional historian of the classical mold. Roman and Greek history was a little different than what we expect from the field. Wikipedia suggests a typical approach:

In Roman historiography commentarii is simply a raw account of events often not intended for publication. It was not considered traditional “history” because it lacked the necessary speeches and literary flourishes. Commentarii was usually turned into “history” later on.

A Roman reader would expect the author of a history to present a polished account rather than a word-for-word stenography. Given the expense of the two volumes Theophilus commissioned, he would have demanded the high literary quality that Luke did, in fact, deliver. Therefore, Peter's sermon in Acts 2 was likely "punched up" a bit.¹

We know that Luke used a number of sources. Luke's version of Jesus' genealogy and the details of the Nativity which seem known only to Mary² suggest that Mary herself was one of Luke's sources. If so, we may conclude that Mary relayed the Magnificat to Luke and he wrote it down. In all likelihood, she would have recited it 30 or more years after the event in Aramaic. So we aren't reading a teenage girl's poem, but a Greek translation of psalm from the heart of a widow who has outlived her oldest son.

This is not to say that Mary could not or did not compose the canticle that we read (modulo translation, of course) nor that it was remembered from her youth. Rather, we ought not be surprised by the literary quality of soliloquies in the Bible and especially in Luke's works. Ancient writers were far more concerned about the essence of history than its substance. Without a doubt, Luke portrays the pregnant Mary as wise beyond her years. The song he provided her with reflects that reality.

---

Footnote:

1. Or maybe not since he was inspired by the Holy Spirit at the time. But the point is, Luke didn't have a tape recording to transcribe and he likely did not have the precise words of the sermon. Rather he gathered one or more accounts of what was said, quoted some relevant Scripture, and "reconstructed" the speech.

2. Particularly:

   But Mary treasured up all these things, pondering them in her heart.—Luke 2:19 (ESV)