In terms of our relationship with God, Martin Luther “has very, very limited use, if any use at all, for reason”.  How can this be true? We are made in the image of God. Part of our being is our reasoning ability. Did God give us this ability and yet totally ignore it when it comes to our relationship with him?
Now I agree we need God’s revelation given through the Bible and Jesus. There is no way using only our reason that we can know and understand God’s plan for us. However, even though our definitive communication with God is the Bible, how can we properly interpret the Bible unless we use reason? There are two examples.
First, there are conflicting passages in the Bible about what constitutes salvation. Most Christians believe salvation is through belief in Jesus alone but there are over 70 verses that teach salvation is through the person we become. How do we resolve this issue? We must use reason.
Second, from my experience, people who oppose the use of reason in our relationship with God believe they have the correct interpretation of the Bible and therefore they think they have no cause to use reason. Everyone agrees that God made us finite. What does it mean that we are finite? It means that we are limited in our ability to know what is true. If we are finite, how can we be sure our interpretation of the Bible is correct unless we use reason and dialogue with other Christians?
Reason is absolutely essential in our Christian life. Martin Luther was finite just like the rest of us and in this case he is in error.
 Carl Trueman, “Self-glory or a cross?”, World Magazine, September 30, 2017, p. 24.