By Bryce P Wandrey
“Concerning free will it is taught that a human being has some measure of free will, so as to live an externally honourable life and to choose among the things reason comprehends. However, without the grace, help, and operation of the Holy Spirit a human being cannot become pleasing to God, fear or believe in God with the whole heart, or expel innate evil lusts from the heart. Instead, this happens through the Holy Spirit, who is given through the Word of God.”  So reads the eighteenth article of the Augsburg Confession. In these words of Melanchthon, one finds a concise statement of the Lutheran understanding of the power, and powerlessness, of human reason.
Martin Luther made a distinction between reason before the Fall, after the Fall in general, and reason in a regenerate person. “…The gift of ratio in Adam constituted the image of God prior to the fall. …Humans could know God by means of reason.” As witnessed both in his Disputation Concerning Man (1536) and his Lectures on Genesis, Luther believed that ratio was the greatest and most important of God’s gifts.
The fall of Adam did not abolish this gift. After the fall, reason continues to constitute humanity’s uniqueness in the created world, the specific difference that distinguishes humans from animals and gives humans their peculiar position between angels and beasts. Reason enables humans to reflect and to understand, and consciously to situate present reflection historically. Reason is instrumental in the development of science: for example, it enables humans to count days and years and, in general, to relate to time. Further, reason, according to Luther, “is the soul of law and mistress of all laws.” He sums all this up: “Nor did God after the fall of Adam take away this majesty of reason, but rather confirmed it.” Elsewhere he adds: It is certainly true that reason is the most important and the highest in rank among all things and, in comparison with other things of this life, the best and something divine.”
How then is reason impacted by Adam’s fall? It is affected both in its self-perception and in the extent of what it can know. In an Epiphany sermon (on Isaiah 60.1-6), Luther admits that in the realm of temporal affairs “the rational man is self sufficient: here he needs no other light than reason’s.” Within the temporal realm, reason can see that good is to be promoted and evil avoided. The problem is that man uses it and prides himself in what it accomplishes without remembering that it is a gift that originated with God. Since the Fall reason serves for the self-glorification of man.
By itself, reason can even know of God’s existence. This knowledge, however, is deeply ambiguous and uncertain. Luther reaffirmed the assertion of St. Paul in Romans 5.10: God is known through his works of creation.  But he also stated, in The Bondage of the Will, that “God governs the external affairs of the world in such away that, if you regard and follow the judgment of human reason, you are forced to say, either that there is no God, or that God is unjust.” 
In general, however, Luther did affirm that humans continue to have a twofold knowledge of God. In Lectures on Galatians (1535) Luther explains that these are 1) a general and 2) a particular knowledge. General is that knowledge that all men have that God created heaven and earth and that he is just and shall punish the wicked. The particular is that knowledge of what God thinks of man and what he plans to do/has done to deliver man from his sin. These things are not known naturally to man. Here is the distinction between reason and faith, which Luther summarize as follows: “Apart from Christ there is nothing but sheer idolatry, an idol and a false fiction about God, whether it is called the Law of Moses or the law of the pope or the Koran of the Turk.”
In matters strictly pertaining to salvation, reason remains completely blind. It does not recognize the goodness hidden underneath the offensiveness of the Cross. It seeks salvation by means of the works of the law. And it attempts to penetrate the hiddenness of the Divine Majesty, rather than see God revealed in Christ. In Lectures on Galatians, Luther states: “Reason cannot think correctly about God; only faith can do so. A man thinks correctly about God when he believes God’s Word. But when he wants to measure and to believe God apart from the Word, with his own reason, he does not have the truth about God in his heart and therefore cannot think or judge correctly about Him.” Reason is limited due to the fact that, without divine revelation, reason cannot tell what the good and what the evil actually are when it comes to the divine-human relationship. So, although it can practice some autonomy and freedom, reason is still in chains within the temporal realm when it comes to discerning good and evil in relation to God. While Luther gives reason, in its natural abilities, the power to reach as far as knowing God as kind and gracious, that is as far as he is willing to go. Reason falls short on two points: first of all, although reason can attain the knowledge that God can aid man, it does not believe that he will do so; and secondly, though reason knows that God exists, it does not know who or what God is. Reason is given temporal autonomy by Luther, even called God’s most precious gift by him, until it begins to impinge upon the affairs of God. 
When it comes to salvation, reason is not only useless but also misleading. Reason is bound by the limitations of this sinful world. In being so, it shuts itself off from the Word of God and from faith in that Word. Reason views God’s plan of salvation for humanity as an absurdity and an impossibility as evidence by St Paul: “We preach Christ crucified, a stumbling block to Jews and folly to Gentiles” (1 Cor 1.23). Hence Luther: “It is up to God alone to give faith contrary to nature, and ability to believe contrary to reason. …Reason turns away from faith.” Reason views faith and the salvific plan of God in this light because it is left to its own devices which results in works righteousness. “Human nature, corrupt and blinded by the blemish of original sin, is not able to imagine or conceive of any justification above and beyond works.”
The words of Christ could never be grasped by reason, but only by faith. Even if reason knows of God’s existence, it still does not know of His will toward humanity. Scripture must be man’s guide in the godly realm, not reason. In his Disputation Concerning Man Luther writes: “Nor is there any hope that man in this principal part can himself know what he is until he sees himself in his origin which is God” and “He can be freed and given eternal life only through the Son of God, Jesus Christ (if he believes in him)”. Indeed, according to Robert Kolb, Luther’s understanding of revelation in God’s Word is primarily determinative of his theology and is one of the lasting fundamentals of his legacy:
God reveals himself in such a way that human creatures are totally dependent on his Word, which Luther contended can be found alone in Scripture (and human conveying of its message). Therefore, in what he called the ‘theology of the cross,’ he not only affirmed the atonement wrought through Christ’s death and resurrection but also the distinction between the Hidden God, inaccessible to human reason, and the Revealed God, whom faith grasps as it is created by God’s revelation of himself in Christ and in Scripture.
What about reason in the regenerate? Paul Althaus observes that through hearing the Word of God reason is regenerated and is one and the same essence as the original creation of God. In consequence of a person’s regeneration, reason now allows itself to be informed by faith and held captive by God’s Word. It becomes theological and helps humanity to understand and explain Scripture.
Luther’s understanding of reason is summed up nicely by Gerrish: In all his dealings with the world man’s guide is reason: the world is the Kingdom of Reason, and by his God-given understanding and wisdom man is able to subdue the earth and have dominion over the beasts of the field. In his dealings with God, however, only faith can be man’s guide, specifically, faith in ‘the Word’ or in Christ.
“The Augsburg Confession,” Article XVIII.1-3. The Book of Concord, (Robert Kolb and Timothy J Wengert, ed.), (Minneapolis: Fortress Press, 2000).
 Bernhard Lohse, Martin Luther’s Theology: Its Historical and Systematic Development, (Minneapolis: Fortress Press, 1999), 197.
 Lohse, 196-97. Cf. Luther’s view on reason as part of the image of God in Lectures on Genesis.
“This positive assessment should not be taken as Luther’s absolute judgment on reason prior to the fall though as he could also put forward the thought in The Bondage of the Will that “God is absolutely incomprehensible in omnipotence and righteousness.” Lohse, 197.
 Gerrish, 13.
 LW 34:137. [Luther’s Works (American Edition: 55 Volumes), J. J. Pelikan, H. C. Oswald & H. T. Lehmann, Ed., (Minneapolis and St Louis: Augsburg Fortress and Concordia Publishing House). From now referred to as LW and volume number.]
 LW 34:137.
 Quoted by B.A. Gerrish, Grace and Reason: A Study in the Theology of Luther, (Oxford, UK: Clarendon Press, 1962), 12.
 Paul Althaus, The Theology of Martin Luther, (Philadelphia, PA: Fortress Press, 1966), 65-66.
 Althaus, 15.
 trans. J.I. Packer and O.R. Johnston (Westwood, NJ: Fleming H. Revel, 1957), 315.
 LW 26:399.
 LW 26:400-01.
 LW 26:238.
 “A theologian of glory calls evil good and good evil. A theologian of the cross calls the thing what it actually is. …He who does not know Christ does not know God hidden in suffering. Therefore he prefers works to suffering, glow to the cross, strength to weakness, wisdom to folly, and, in general, good to evil.” LW 31:53.
 Gerrish, 15, 17.
 LW 34:160.
 LW 34:151.
 Gerrish, 17-18.
 LW 34:138.
 “Luther in an age of confessionalization,” The Cambridge Companion to Martin Luther, ed. By Donald K McKim, (Cambridge, UK: Cambridge University Press, 2003), 223.
 Althaus, 70-71.
 Gerrish, 26.