Simeon's Prophecy
In his book, Images of Judaism in Luke-Acts, Joseph B. Tyson claims Simeon's speech sets the stage in Luke-Acts on how the Jewish people will respond to the message of Jesus as Christ:
As an anticipation of the relation of the Christian message to Judaism,[emphasis added] the speech of Simeon in Luke 2:29-35 is the key passage in Luke 1-2. Indeed, it serves as a significant anticipation of a number of themes that will find expression later in Luke-Acts.1
Tyson agrees with Raymond Brown and others that Simeon's speech should be divided into two parts.2
The first affirms the promise Simeon would see the Messiah before he died. The second is this prophetic warning:
...the child Jesus is to be the cause of the fall and rise of many in Israel, and he is to be a sign that brings controversy and rejection among the Jews. The text requires us to understand that controversy and rejection of Jesus' message will occur within Israel; there is no suggestion that there is such a controversy among the Gentiles.3
This follows what Jesus said He would cause to happen:
51 Do you think that I have come to give peace on earth? No, I tell you, but rather division. 52 For from now on in one house there will be five divided, three against two and two against three. 53 They will be divided, father against son and son against father, mother against daughter and daughter against mother, mother-in-law against her daughter-in-law and daughter-in-law against mother-in-law.” (Luke 12) [ESV] (also Matthew 10:35-36)
Mary's Piercing
Mary was not immune from the controversy and/or rejection and their effects:
31 And his mother and his brothers came, and standing outside they sent to him and called him. 32 And a crowd was sitting around him, and they said to him, “Your mother and your brothers are outside, seeking you.” 33 And he answered them, “Who are my mother and my brothers?” 34 And looking about at those who sat around him, he said, “Here are my mother and my brothers! 35 For whoever does the will of God, he is my brother and sister and mother.” (Mark 3) (also Matthew 12:46-50 Luke 8:19-21)
The Gospel is silent on their purpose, who "His family" included, or their reaction to His words. But Mark and John make explicit reference to the initial rejection within Jesus' (and so Mary's) family:
And when his family heard it, they went out to seize him, for they were saying, “He is out of his mind.” (Mark 3:21)
For not even his brothers believed in him. (John 7:5)
It is true some would believe (their rising) after Jesus' Resurrection, yet it is easy to see how the family's, relative's, and friend's immediate response to Jesus (their falling) would create division within these groups which would "pierce" Mary.
Mary's piercing should not be limited to the period of the Gospel, but should also include the type of reaction Paul expresses (the period of Acts) over Israel's partial acceptance of the Christian message:
1 I am speaking the truth in Christ—I am not lying; my conscience bears me witness in the Holy Spirit— 2 that I have great sorrow and unceasing anguish in my heart. 3 For I could wish that I myself were accursed and cut off from Christ for the sake of my brothers, my kinsmen according to the flesh. 4 They are Israelites, and to them belong the adoption, the glory, the covenants, the giving of the law, the worship, and the promises. 5 To them belong the patriarchs, and from their race, according to the flesh, is the Christ, who is God over all, blessed forever. Amen. (Romans 9)
There should be little doubt Mary experienced both the problems of dealing with the immediate impact controversy brings to any family and the type of feeling Paul expresses as a believer mourning over relatives and loved ones who rejected the Gospel. Perhaps as a mother, her angst would be greater than Paul's.
Conclusion
Tyson agrees with Brown and others who (like the ESV) take the beginning of verse 35 as parenthetical, but they place that in continuity with the previous verse. Therefore, "so that thoughts from many hearts may be revealed” refers to the controversy and rejection Jesus will bring to the Jewish people:
Thus the sword that pierces the life of Mary is the sword of discrimination, discrimination between falling and rising. Says Brown, "This interpretation makes Simeon's prophecy of discriminatory judgment for Israel applicable to Mary as an individual Israelite, and more specially applicable to her as a member of Jesus' family...The child is set for the fall and rise of many in Israel (34c); but, as the emphasis on "fall" indicates, for the majority he is a sign that will be contradicted (34d) since, as they face him, the hostility of their inmost thoughts toward him will be revealed (35b)."4
Notes:
1. Joseph B. Tyson, Images of Judaism in Luke-Acts, University of South Carolina Press, 1992, p. 49
2. Raymond Brown, Birth of the Messiah: A Commentary on the Infancy Narratives in Matthew and Luke, Doubleday and Co., 1977 as cited in Tyson, p. 49
3. Tyson, p. 51. [If "message" is not limited to Jesus but includes that from the Apostles, "Israel" should be "Israelites" as the same responses are found in Jewish communities outside of Israel.]
4. Brown as cited in Tyson p. 52