DD, When was Christianity determined to be solely reliant on the scriptures? I know you are quoting Martin Luther, but are you following Luther or of Jesus?
The reason I ask is this: Luther was reacting to the Catholic Church's various accretions to the word of God. Like indulgences.
But even the Apostles had to deal with sorting the Law of Moses from the new Christian freedom. Acts 15:28,29 cut out a lot of scripture. I'll bet there were slews of newly minted Christians that were in divine ignorance of all they were missing--(though the big issue they knew about involved a sharp bit of flint)
Did the apostles ignore the scriptures, did they reject the word of God?
When the Bible talks about us having the "mind of Christ", what does it mean?
What practical information is there for you or me in using a word like predestination and pretending we know how it works?
Church Fathers on the doctrine of predestination
The early church fathers consistently uphold the freedom of human choice. This position was crucial in the Christian confrontation with Cynicism and some of the chief forms of Gnosticism, such as Manichaeism, which taught that man is by nature flawed and therefore not responsible for evil in himself or in the world. At the same time, belief in human responsibility to do good as a precursor to salvation and eternal reward was consistent. The decision to do good along with God's aid pictured a synergism of the human will and God's will. The early church Fathers taught a doctrine of conditional predestination. 
Augustine of Hippo marks the beginning of a system of thought that denies free will and affirms that salvation needs an initial input by God in the life of every person. While his early writings affirm that God's predestinating grace is granted on the basis of his foreknowledge of the human desire to pursue salvation, this changed after 396. His later position affirmed the necessity of God granting grace in order for the desire for salvation to be awakened.
Augustine's position raised objections. Julian bishop of Eclanum, expressed that Augustine was bringing Manichee thoughts into the church  . For Vincent of Lérins, this was a disturbing innovation.  This new tension eventually became obvious with the confrontation between Augustine and Pelagius culminating in condemnation of Pelagianism (as interpreted by Augustine) at the Council of Ephesus in 431. The British monk Pelagius denied Augustine's view of "predestination" in order to affirm that salvation is achieved by an act of free will.
The influence of Augustine also then showed in translations of the bible from that time on; variations which are not in themselves visible in the syntax or grammar of the New Testament Greek text. Perhaps the best example of this in the Vulgate is the addition of 'prae' to 'ordinati' in Acts 13:48 which is there only to give the idea this was God who did this. Later translations show this influence of the doctrine by the additions of the word 'his' in Romans 8:28 and 11:22 all suggesting an interpretation consistent with unconditional election.
Augustine's formulation is neither complete nor universally accepted by Christians. But his system laid the foundation onto virgin ground for the then later writers and innovators of the Reformation period.