If I don’t take into account Luther’s underlying presupposition of the hidden and revealed God, I will make some blatant errors against his theology. I could make all sorts of web pages proving Luther was a 5-point Calvinist. I could even find a lot of secondary sources to prove it. But, I would be doing injustice to Luther’s work. I would be manipulating his material to prove something that is untrue (Which reminds me, one of my favorite authors, RC Sproul has said a few times something like: “Luther spoke more about predestination and election than Calvin ever did...”- I find this statement to be in error, having read both Calvin and Luther extensively myself).
Reading Luther accurately requires reading Luther according to his own theological paradigms, particularly a basic understanding of his use of contrast and paradox. Luther repeatedly exhorts his readers not to probe into the secret council of the "hidden God. However, what are those things which should not be probed? Luther lets us know it’s the deep mysteries of providence, election and reprobation. On the other hand, to only look at Luther’s understanding of the "revealed God" does not give us an adequate picture of Luther’s paradox of the "hidden/revealed God." One does not understand Luther's paradox without probing both sides to see what he means.
My understanding is that Luther did indeed attribute double predestination to the "hidden God." To prove this, I'd like to quote a section from: Paul Althaus, The Theology of Martin Luther (Philadelphia: Fortress Press, 1966). I consider this book crucial to any study of Luther:
“For Luther the assertion that God is God implicitly includes the fact that God alone works all in all together with the accompanying foreknowledge…. This determines not only man's outward but also his inner fate, his relationship to God in faith or unfaith, in obedience or disobedience. Here too man is completely in God's hands. Luther finds the biblical basis for this particularly in I Corinthians 12:6, "God works all in all." Luther expands the sense of this passage far beyond Paul's meaning in its original setting. It appears very frequently in Luther's thought.
The Bible in addition bears witness, and experience confirms the fact, that men actually relate themselves differently to the word of God. Some are open to faith; others remain closed to it. Accordingly, the Bible expects human history to end in a twofold way. Not all will be blessed; and many will be lost. Luther can, in the context of his assertion that God works all in all, find the ultimate cause in God himself, in his intention, and in his working. This decision is not made by man's supposedly free will, but only by God's willing and working. He chooses some to be saved and he rejects the others without an apparent reason for either choice. He gives faith to one through the working of His Spirit; and he refuses to give faith to others so that they are bound in their unbelief. Salvation and destruction thus result from God's previous decision and his corresponding twofold activity. God's choice is not based on the individual's condition; it establishes this condition. This means an unconditional, eternal predestination both to salvation and to damnation.
Luther does not reach this conclusion on the basis of philosophical speculation about God, but finds it in the Scripture. He experienced it in God's relationship to him personally; and the God whom he thus personally experienced is the very same God who speaks and is proclaimed in the Scripture. Paul especially testified to Luther that God makes this twofold decision and that he hardens those who are lost: "God has mercy upon whomever he wills, and he hardens the heart of whomever he wills" (Rom. 9:18). Paul illustrates this with the picture of the potter making vessels of honor as well as dishonor out of the same clay (Rom. 9: 20 ff.). In addition, Paul quotes Malachi, "Jacob I loved, but Esau I hated" (Rom. 9:13). And Paul specifically refers to God's treatment of Pharaoh (Rom. 9:17)
The position Scripture thus presented to Luther was also the inescapable result of his understanding of God. He even cites man's innate rational concept of God as an additional proof. It seems blasphemous even to think that God does not work man's decision to believe or not to believe, as though God could be surprised by man's choice and men might be saved or lost without God knowing it. Whoever so thinks denies that God is God and makes fun of Him as though he were a ridiculous idol." Whoever speaks seriously of God must necessarily teach his foreknowledge and his unconditional determination of all things.
Luther thus finds a twofold will of God in the Scripture. Together with statements about God's all-inclusive grace are other statements which express another willing and working of God which stands with his willing and working of salvation. Together with grace stands wrath, a wrath which rejects and which is no longer a part of love; and this is found not only in the Old but also in the New Testament. Luther did not draw a two-sided picture of God from his own imagination, but he saw it already present in Scripture. The God of the Bible is not unequivocally the God of the gospel. The God of the Bible is not only the God of all grace but is also the God who, if he wills, hardens and rejects. This God even treats a man equivocally: he offers his grace in the word and yet refuses to give his Spirit to bring about his conversion. He can even harden a man—in all this Luther does not go in substance beyond the difficult passages of Scripture which describe God as hardening a man's heart.
Luther, however, summarized the substance of such scriptural statements in the sharpest possible expressions. In The Bondage of the Will he teaches that God has a double will, even a double reality. The God revealed and preached in the gospel must be distinguished from the hidden God who is not preached, the God who works all things. God's word is not the same as "God himself." God, through his word, approaches man with the mercy which (according to Ezekiel 33) does not seek the death of the sinner but that he turn and live. But the hidden will of God, the will we must fear, "determines for itself which and what sort of men it chooses to enable to participate in this mercy offered through the proclamation." God "does not will the death of the sinner, that is, according to his word; he does, however, will it according to his inscrutable will." God revealed in his word mourns the sinner's death and seeks to save him from it. "God hidden in his majesty, on the other hand, does not mourn the sinner's death, or abrogate it, but works life and death in everything in all. For God has not limited himself to his word but retains his freedom over everything. . . . God does many things that he does not show us through his word. He also wills many things his word does not show us."
Source: The Theology of Martin Luther 274-276