pteranodon, Your question is vast. It covers at least two doctrines in the bible—Conversion and Justification, each of which deserves much time in explaining. But, if you are willing, I'd like to tackle your query.
Defining Decision Theology
Divine Monergists (Lutherans & Calvinists) use the term "decision theology" to describe a particularly Arminian view of conversion in which a person is confronted with Jesus (who he is and what he has done for that person) and then makes use of his will (makes a decision) to be a Christian or not. Years ago the Southern Baptist Convention put out a pamphlet which pictured conversion this way: God has cast his vote; he wants you in heaven. But Satan has also cast his vote; he wants you in hell. You have the ability to cast the 'tie-breaker'. What will your vote (decision)be? If you'd like a current explanation of this, just look at the SBC website:
A. Regeneration, or the new birth, is a work of God's grace whereby believers become new creatures in Christ Jesus. It is a change of heart wrought by the Holy Spirit through conviction of sin, to which the sinner responds in repentance toward God and faith in the Lord Jesus Christ. Repentance and faith are inseparable experiences of grace.
Repentance is a genuine turning from sin toward God. Faith is the acceptance of Jesus Christ and commitment of the entire personality to Him as Lord and Savior. (http://www.sbc.net/bfm2000/bfm2000.asp)
Notice in this explanation of conversion the Holy Spirit terrifies you as you become aware of your sin and the consequences of sin (hell). Then you respond (decide) toward God. So also, in the next paragraph one 'accepts' (decides) to commit himself to Jesus.
When Lutherans use the word, 'conversion' we speak of that instant and moment in which a person is an unbeliever and then is given faith to both know and trust in the Triune God. I make this distinction since many especially in evangelical/arminian church bodies make becoming a Christian a process. For Lutherans there is an instant and a moment in which a person is an unbeliever and then becomes a believer.
In conversion, God uses his word to create faith in a person's heart. God is the one who chooses a person and creates faith in his heart through his word. A person is not able to use his will in conversion because, through the fall into sin, his will is the very thing that needs to be converted. In showing this from scripture two points are usually made to back this up from scripture:
- The far-reaching effects of sin (so that a person is dead, blind, an enemy of God, without any ability to know God or come to him and decide for him): Is 65:1; Mt 7:18; Lk 6:43,44; Jn 3:6; 6:44; Ro 3:11; 8:7; 10:20; 1 Cor 2:14; 12:3; Eph 2:1; Col 1:21; 2:13
- Conversion is entirely a work of God: 1 Peter 1:23; Rom 10:17, James 1:17-18; Ac 11:21; Jn 6:44; 1 Cor 12:3; Philip 2:13; Col 2:13; Dt 29:4; Jr 32:39; Eze 36:26; Ac 26:16–18; 2 Cor 4:6; Eph 1:17; 2:5; Philip 1:6; 2:13.
For an exhaustive treatment of this, I invite you to walk through Article II in the Formula of Concord: (http://bookofconcord.org/sd-freewill.php)
Lutherans have always upheld the doctrine of Justification. Justification is the teaching in the bible that one is "declared not guilty" or "declared righteous" in Christ. The doctrine of Justification has an objective and subjective sense to it. Objectively God has declared the entire world 'not guilty.' (Rom 3:20-24;4:5;5:16,18; 2 Cor 5:18, 1 Pet 3 18, 1 John 2:2, 2 Peter 2:1 et al) Subjectively, God has declared individuals (me!) not guilty (Gal 2:20; Mt 9:2; Lk 7:47,48; 18:14).
Again, the book of Concord is an excellent resource to look into this further: (http://bookofconcord.org/sd-righteousness.php)
Where these two doctrines come together and are criticized by many Evangelicals/Arminians is the deduction that if God chooses people and declares the world 'not guilty', then everybody must get into heaven. This is not what Lutherans teach. While the credit for being being justified and given faith is given to God (and him alone), it is possible for a person to be given faith and then fall away. For God's word is powerful, but not irresistible. In this case the cause and blame for being an unbeliever (and ending up in hell) is the person's, not God's.(Jr 15:7; 25:5,7; 35:15,17; Ho 11:5,6—Mt 23:37; Ac 7:51; 2 Chr 24:19; 30:6–10; 36:13; Ne 9:29; Jr 5:3–5; Jr 23:14; Eze 13:22;) Again, the above two articles cited from the book of Concord give a more exhaustive treatment of this. And it might be good to back up even further and walk through article I (original sin) too.
Your question does also deal with the doctrine of election too. But, I thought this would be a decent beginning in answering your question. The doctrine of election is covered in Article XI in the formula of Concord (http://bookofconcord.org/sd-election.php) And, I thoroughly encourage you to read through that at well. It does a beautiful job of bringing so many of these issues together.
Pastor Steve Bauer (http://stevebauer.us)