"Come now, and let us reason together, saith the LORD: though your sins be as scarlet, they shall be as white as snow; though they be red like crimson, they shall be as wool." -- Isaiah 1:18
The ability to reason is a natural attribute of God. He exercised reason in planning the creation of the heaven and earth. He observed His creation and declared it to be good. He created man in His own image with a mind capable of thinking and observed that everything He created was very good. He challenges man to sit down and think together with Him concerning the folly of sin and the way of deliverance from its power.
God has always behaved rationally and he expects man to function in the same manner. If we are to love God with our mind as Jesus commanded (Matthew 22:37), then faith can never be contrary to reason. Sometimes reason may not comprehend the way of faith, but there is also so much that science accepts that it cannot understand or explain. We have good reason to believe that the few apparent contradictions in the Bible are not actual contradictions, but merely appear to be because of lack of understanding on man's part or possibly scribal errors.
What about miracles? Having observed the obvious existence of the Creator in his wondrous and intricate universe, it would be absurd for a man to think, that God could not at times set aside the laws of nature and perform the supernatural. Or perhaps, sometimes the Omnipotent God operates according to a higher law that man has not discovered. Air travel was considered impossible until man understood the laws of aerodynamics.
"But sanctify the Lord God in your hearts: and be ready always to give an answer to every man that asketh you a reason of the hope that is in you with meekness and fear:" -- 1 Peter 3:15
We are challenged to logically defend our hope so faith cannot conflict with reason or God would require the impossible which would be irrational. Only when we reason from false premises, or make faulty inferences from true premises, does reason conflict with faith. Many have faith confused with credulity and fanaticism which is believing something without evidence or reason.
Much of what has passed for Christian doctrine is contrary to reason and Biblical revelation such as the Calvinistic doctrine of predestination. Such a God would not be rational, but arbitrary. False notions about God and His ways are a result of failing to sanctify Him in our hearts. To sanctify God in our hearts is to separate Him from any evil purpose and think just notions of His nature and character.
Faith is the will's reception of the Truth. Unbelief is the will's rejection of obvious Truth. Unbelief is a mortal sin because all men intuitively know God (Roman 2:14-15), and Nature reveals both His existence and goodness so that "they are without excuse." (Roman 1:18-20). Intellectual skepticism is the will's choice to be governed by wild imaginations instead of reason. When a man is dominated by his imaginations instead of reason, he will not think clearly. Sin darkens the mind to the Light.
Noah Porter, president of Yale College, said in 1878, "The position which we occupy is that the Christian faith is the perfection of human reason; that supernatural and historical Christianity is the only Christianity which is worth defending or which is capable of being defended on the grounds of reason or history; and that such Christianity, when interpreted by enlightened judgment, as to its truth and precepts, is not only friendly to the highest forms of culture, but is an essential condition of the same."
In three words: God is reasonable.