"The fear of the Lord is the beginning of knowledge;
fools despise wisdom and instruction." Proverbs 1:7 (ESV)
The Triune God is the fountain head of knowledge. Out of His Being flows knowledge itself. Therefore, to reject the Almighty is to reject the foundation for knowledge.
Let's elaborate on this. Reason is what we call a universal, and a universal does not need a physical object to exist. For example, I use reason when I write this blog, but, if I die, reason does not cease to exist. Reason does not cease to exist when I die physically because it is is not bound by the physical universe due to the fact that its source is God. This assumption is based on a worldview where universals really exist in a concrete yet immaterial manner. That is to say that they flow from God Himself, who is concrete yet immaterial. He is concrete (do not think of concrete in this illustration as physical material) in that He exists, yet He is immaterial in that He is not bound by the physical world that He created.
However, in a purely materialistic worldview where the world is only matter, one's ability to account for the reliability of reason has ceased. Why? If reason is dependent on the electro-chemical impulses in my brain, as the late Dr. Greg Bahnsen would say, then it ceases to exist if every brain stops transmitting electro-chemical impulses because, in this worldview, reason is forcible bound by the material world if the world is only material. This is a serious problem because reducing reason to a material object makes its universality a mere illusion at best.
How does all of this play out in everyday life? The Christian worldview accounts for reason because it flows from the very Being of God, so a Christian can trust that reason is real and not a mere illusion. This gives him the freedom to make real choices like deciding what to eat for breakfast. He really does have the freedom to decide to eat eggs and bacon or just eat cereal with milk. He is not a mechanistic robot that is bound by the pre-determined electro-chemical impulses of his brain. Man is given only a certain amount of freedom within the Sovereignty of God, but man is empowered with the ability to make real choices that are not mere illusions of the ability to freely act upon the world around him. That freedom is fallen and bound to sin (see related posting on man's total depravity), but it does exist.
Why then does a mental malfunction occur when brain damage occurs? Human beings are knit together by God, according to the Bible, as both material and immaterial, and both affects each other. If I get brain damage, that will impact the ability of my immaterial mind to operate rightly upon the vehicle of the physical brain. This is because our immaterial nature is woven together with a physical nature. However, when I die physically, I will be with the Lord immediately and any brain damage will be of no more effect because my immaterial nature will have been set free from a broken material body that inhibited my mind from functioning properly. This is not the end because man was created to glorify God within a physical and immaterial existence. For this reason, God will make a glorified body for me that is rejoined with the immaterial that will enable me to function in a marvelous way that will give me great freedom to worship God beyond a comprehension that I cannot now even begin to grasp!
For the materialist, man is a robot. This mechanistic and fatalistic religion has no choice but to deny man from making genuine free choices in acting upon the world around him. The end of this worldview is devastating. Even seeing that fact is but an illusion. Even recognition that it is but an illusion cannot be substantiated.
Therefore, it is futile for the atheists to argue against Christianity within the materialistic worldview because both the atheist and the Christian would then be predetermined to think a certain way based on their respective predetermined electro-chemical impulses. Any arguing for the atheist's worldview immediately magnifies the futility of the debate because the atheist would be incapable of persuading the Christian to become an atheist. This is why materialism leads to nihilism or what is called the zero point (see James Sire's book The Universe Next Door for a basic intro into nihilism), which is the point at which any effort to substantiate even reason itself has ceased.
Where then does this nihilism lead us? Nietzsche is called the post modern prophet because he embraced this dilemma and advocated that everyone should attempt to traverse to and through nihilism. The only problem is that this creates purpose that is necessitated by a free will that does not exist within this kind of world. Nevertheless, this worldview has entrenched itself into Western thought and ushered in an era of relativism where anything goes because absolutes (ie universals) are an illusion. Ironically, that is an absolute statement that shows just how quickly this worldview self-destructs.
Man now touts relativism, but what he really does is create a set of principles to live by for what he determines is good for him. He looks into the black hole of nihilism and refuses to jump in, so man absurdly asserts that he has freedom to choose his own way yet deep down realizes that this freedom and the recognition of it is only an illusion (existentialism, see Sire for a basic understanding of this).
In conclusion, it is no wonder why the Psalmist proclaims, "The fool says in his heart, 'There is no God.' " (first line of Psalm 14:1) Living in practical atheism (see note in ESV Reformational Study Bible on this verse) leads man to despair. Man, in his hard of hearts, would rather embrace absurdity in a futile effort to exalt himself rather than submit to a Holy God that can free him of his irrational idolatry that has taken many forms since Adam! That is what we face everyday when we evangelize! This is why manipulative evangelistic methods are ridiculous and insulting to the Only One Who can set man free from his depravity! Praise Him when a soul is set free by the regenerating power of the Holy Spirit! Amen!