What does it mean that God effectively calls and converts us?
"Effectual calling" is the title of ch. 10 of the Westminster Confession (1647). The chapter begins: All those whom God hath predestinated unto life, and those only, He is pleased, in His appointed and accepted time, effectually to call, by His Word and Spirit, out of that state of sin and death, in which they are by nature, to grace and salvation, by Jesus Christ; enlightening their minds spiritually and savingly to understand the things of God, taking away their heart of stone, and giving unto them a heart of flesh; renewing their wills, and, by His almighty power, determining them to that which is good, and effectually drawing them to Jesus Christ: yet so, as they come most freely, being made willing by His grace.
What is described here is the process of Christian conversion, involving illumination, regeneration, and the transformation of the will.
It is a sovereign work of God, "effectually" (that is, effectively) performed by the power of the Holy Spirit. The doctrine corresponds to Paul's use of the word "call" in the sense of "to bring to faith," and his use of "called" to mean "converted" (Rom. 1 :6; 8:28, 30; 9:24; 1 Cor. 1 :9 , 24, 26; 7:18, 21 ; Gal. 1 :15; Eph. 4:1, 4; 2 Thess. 2:14). This calling is different from the general invitation, as described in Jesus' explanation of the parable of the wedding feast (Matt. 22:14).
The general, external invitation can fail to be answered, but the effectual calling is a particular act of God resulting in regeneration. It cannot be refused (John 10:3, 4). Original sin means that all human beings are by nature "dead," or unresponsive to God. Through the effectual calling, God gives life to the dead. The outward call of God to faith in Christ is communicated everywhere through reading, preaching, and explaining the gospel.
In the inner, effectual call the Holy Spirit enlightens the mind and renews the heart of those God has chosen so that the gospel is accepted as the truth of God, and God in Christ becomes the object of love and affection. When once regenerated and having the will set free to choose God and the good, a sinner turns away from the former pattern of living and receives Jesus Christ as Lord and Savior, to start a new life with Him.