Acts 16:14

Acts 16:13-15 (see also 2nd Corinthians 3:14-16Acts 26:15)
And on the Sabbath day we went outside the gate to a riverside, where we were supposing that there would be a place of prayer; and we sat down and began speaking to the women who had assembled. A woman named Lydia, from the city of Thyatira, a seller of purple fabrics, a worshiper of God, was listening; and the Lord opened her heart to respond to the things spoken by Paul. And when she and her household had been baptized, she urged us, saying, “If you have judged me to be faithful to the Lord, come into my house and stay.” And she prevailed upon us.

​Question: What does it mean that God “opened” 
her heart?

Answer: God helped Lydia to understand Paul’s 
message so that she could respond to it, rather than 
making her respond, as there was no need to force 
her, given that she was already a receptive 
worshiper of God,” rather than a totally depraved, 
totally unable, hater of God. Jesus appointed Paul 
as a minister and a witness to the Jews and 
Gentiles for this very purpose, that is, to “open 
their eyes.” (Acts 26:15-18) This should not be 
understood any differently than when Jesus 
preached along the Road to Emmaus to two 
believers, who then concluded: “They said to 
one another, ‘Were not our hearts burning within us 
while He was speaking to us on the road, while He 
was explaining the Scriptures to us?’” (Luke 24:32) 

John Mason: “She was already a ‘worshiper of God.’ That God must be involved in a spiritual transformation is not in dispute, as we all have a sin nature and are lost. What is at stake is whether or not this verse shows that God forced this individual to move from a position of disbelief to belief. It definitely does not attest to such a fundamental change.” (Calvinism: The Road to Nowhere, p.184, emphasis mine)

Laurence Vance: “...God opening Lydia’s heart didn’t guarantee her salvation any more than all Gentiles being saved because God ‘opened the door of faith unto the Gentiles’ (Acts 14:27).”  (The Other Side of Calvinism, p.505)

So this this passage is shown to be of no use to Calvinists, since she already loved God, and was not a totally depraved, totally unable hater of God who rejected and refused God. 

One Calvinist explains: “Just because someone worships God in the sense of religious observance of the Old Covenant does not mean that they have been regenerated.” (Emphasis mine)

The text doesn’t say that she was claiming to have been a “worshiper of God,” but rather, the text itself asserts that point as fact. Alleging that she was a false worshiper, as a hater of God, is certainly a leap outside of the text, though that would be needed for Calvinists to be consistent.

Calvinist, James White: “If we have libertarian free will, why would God have to open Lydia’s heart to respond to the things spoken by Paul? Is that not a violation of ‘free will’? And if God can open Lydia’s heart, why does He not open every person’s heart in the same way? Shouldn’t the text say that she opened her own heart?” (Debating Calvinism, p.204, emphasis mine)

It wouldn’t be a violation of her free-will if she was already receptive as a “worshiper of God,” and as for why she needed for God to open her heart to respond, the text doesn’t say, and of course, the text also never says that she was forced into anything, but rather enabled. Perhaps all that she needed was a preacher to articulate the gospel in the manner that Paul did, who “spoke in such a manner that a large number of people believed, both of Jews and of Greeks.” (Acts 14:1) After all, Paul was appointed by Jesus as a minister and a witness for this very purpose, that is, to “open their eyes.” (Acts 26:15-18) As for what God does for everyone, John 16:8 indicates that the Holy Spirit convicts the world of its sin. Those who are receptive to the light and welcome God’s grace, tend to receive more light and more grace, and such certainly seems to be the case with Lydia, as a receptive “worshiper of God.” However, Calvinists need to explain why she needed regeneration in her encounter with Paul, if she was already, previously a worshiper of God, which according to Calvinism, would have required a previous regeneration. So are Calvinists forced into teaching progressive regenerations?

​Calvinists cannot admit that she was previously a believer in God, or else their theology would require a double regeneration, that is, one previous to her encounter with Paul, and again during her encounter with Paul.

James White: “God had to take out that heart of stone and put in Lydia a heart of flesh (Ezekiel 36:26) so that she would respond to the message of the Cross.” (The Potter’s Freedom, p.289, emphasis mine)

The text makes no mention of God taking out her old heart of stone, and which would certainly be inconsistent with the fact of what the text actually does state, which is that she was already a “worshiper of God.” It is interesting that when Calvinists read “opened,” they see “take out.” 

John Calvin: “If Lydia’s mind had not been opened, Paul’s preaching would have been mere words.” (The Crossway Classic Commentaries: Acts, pp.278-279, emphasis mine) 

Lydia had been faithful up to the level of revelation that she received, and now she needed to hear the gospel message about the Messiah. It’s not that the gospel message had previously been ineffective on her, or that she had previously rejected it. For all we know, she may not have even heard the gospel yet until Paul arrived.

John Calvin: “Luke shows that we cannot obtain anything merely by hearing the Word, without having the Spirit’s grace; and the Spirit is given to us not to bring contempt of the Word, but to instill confidence in it into our minds and write it on our hearts. If you ask why God only opened one woman’s heart, we must go back to the principle that all those who are preordained to life believe. The fear of God, which in Lydia preceded the clear knowledge of Christ, is also a fruit of election.”  (The Crossway Classic Commentaries: Acts, p.279, emphasis mine) 

No one would ask why God only opened one womans heart and passed by the rest, since the text never elaborates on any such thing.