Christianity is Rational

God is the source of knowledge "The fear of the Lord is the beginning of wisdom and knowledge of the Holy One is understanding" (also see Proverbs 1:7), therefore he is the one that is true sanity, or the Rational One. According to the Christian worldview, humans know anything due to our created capacity to interpret the mind of God as he reveals himself to us, or to put it another way, we know by thinking God's thoughts after Him. The fall had a huge effect on this in that due to sin, we are now incapable of correctly interpreting the revealed mind of God, our epistemological element has become dysfunctional.
This is one reason why humanity is so desperate for Christ, because in Christ we receive the mind of Christ. It is important here to attend to the truth that Jesus was a man, the second Adam (Rom.5). Humanity was given the responsibility to rule creation in God's image as his stewards (Genesis 1:28). They were able to do this because they had the mind of God as their own. In Christ, humans regain this most fundamental trait that defines the very essence of humanity. So we can see Paul's main point in his letter to the Colossians: that Jesus restores to us our humanity.
In John's gospel we read an account of Jesus teaching his disciples. Jesus again is telling them that he must "leave" or die in order to fulfill his vocation. Thomas asks a very natural question, "Lord we do not know where you are going. How can we know the way?" (John 14:5). Jesus gives a very tightly packed answer, "I am the way, the truth, and the life. No one comes to the Father except through me. If you had known me, you would have known my Father also".(vs.6) This verse has commonly been interpreted to mean the way one can get to heaven, that through Jesus is eternal life. This is not a false interpretation, but I believe that such a profound statement also has more to teach us. One of my heroes Cornelius VanTil has seen an epistemological element to this teaching of our Lord. An epistemological element Paul would later expand for us in his letters. The argument can be put as follows:
1. Since sin has disabled our ability to properly interpret the revealed mind of God, we are consequently ALL born naturally irrational (evidenced by the fact the we willingly sin, a most insane and inexplicable activity). 2. As irrational creatures, we must be given back our rationality in order to regain our humanness and proceed with our purpose of thinking God's thoughts after Him and ruling his creation to his glory. 3. The Man, Jesus is the means through which humanity and therefore rationality is restored. Jesus has, through his work, filled the vacant spot left by Adam, due to sin, after the Fall as a rational representative of the human race. Knowing Jesus then allows us once again to know the Father. To know the Creator is to begin to know his creation. In Jesus we have the Way back to knowledge of God (rationality) the Truth about who he is, who we are and what our purpose is in this creation. And we have true Life; we again have our humaness and can now live fruitful lives in the freedom offered in the Gospel.