1. Evolution is driven by survivability of organisms
2. Human brains and senses are the product of evolution
3. Therefore human brains' and senses' existence is driven by survivability- From 1 and 2
4. Beliefs come from the human brain reacting to sense experience
5. Therefore beliefs exist based on assistance to survivability- From 3 and 4
6. Humans believe that God exists
7. Therefore the belief that God exists exists based on its assistance to survivability- From 5 and 6
8. God does not exist
9. Therefore evolution favors false beliefs over true beliefs if the false belief helps survivability more than the true belief- From 7 and 8
10. Therefore the human brain and senses cannot be trusted to yield truth about reality (knowledge)- From 2 and 9
I placed premise 8 in italics because it is the premise that is under debate between atheists and theists. If premise 8 is true then the next two conclusions (really, #10 stated in two more different ways) necessarily follows:
11a. Therefore if naturalism is true, knowledge is not possible
11b. Therefore if knowledge is possible, naturalism is not true
Idiomatically put: we cannot know that we have our naturalistic cake and know that we can eat it too.
Violating the Law of Non-Contradiction
Two things are simultaneously true here: the granting of naturalism assumes the granting of knowledge, but only the denial of knowledge affirms naturalism. Here we have a violation of the law of non-contradiction. Knowledge is both affirmed and denied at the same time and in the same sense in this line of reasoning. Naturalism produces a violation of the law of non-contradiction. Reality does not violate this law. Therefore naturalism cannot be true.
Self-Defeat
Further, premise 8 (God does not exist) requires knowledge not only to make the claim, but to support it via arguments also. However, if premise 8 is true, then the claim of the truth of premise 8 and its supporting arguments are removed via the conclusion (10). The argument destroys itself from within- it is self-defeating. This does not necessitate that God exists, but it does necessitate that if God does not exist, we cannot know that God does not exist. We can only guess and opine that God does not exist.
Hard Agnosticism
If we can only offer guesses and opinions, then this takes agnosticism (not knowing whether God exists or not) beyond just the individual ("soft" agnosticism), but forces it on all of humanity- no one can know whether God exists or not ("hard" agnosticism). If God, indeed, does not exist, then no one can actually know it, and anyone who claims to know that God does not exist, ironically, is lying- not about God's existence, but about their knowledge of it. Since their claim is no more than an opinion, it may be flippantly dismissed or blindly accept as any other opinion without the charge of "academic dishonesty" being true.
Is God Necessary?
Of course, the denial of naturalism minimally includes the acceptance of the metaphysical, but not necessarily a God. Is it possible to affirm a minimal metaphysical realm to retain the ability to know things, yet not go all the way to affirming God's existence? Even with the metaphysical existing, if nothing metaphysical with guiding power can purposefully guide the evolution of the human brain and senses (I'm granting evolution for the sake of continuing the conversation), then we still have the human senses and brain being the products of naturalistic evolution. Its not exclusively naturalism that fails by this critique, it is a specific feature of naturalism that is necessary in naturalism and other worldviews that fails by this critique. If that feature is necessary, but fails by this critique, then so does the worldview fail by this critique.
So if knowledge is going to be possible, we can't get away with merely granting a minimalistic metaphysical reality, we must grant a metaphysical agent that has intelligence and purposefully guided the creation (or evolution) of the human senses and brain to not only aid survivability but to also yield knowledge. . Knowledge necessitates God's existence. If you want to claim that you have knowledge, you cannot escape God's necessary existence. Since knowledge necessitates God's existence, knowledge removes the possibility of naturalism and metaphysical atheism from being true.
Of course, you can easily deny both of those conclusions, by denying that you have knowledge of the falsehood of those conclusions. But you must grant that it is merely opinion that you are offering and is on equal academic and logical footing as is my conclusion that God does exist.
Is Philosophy Dead?
It is no wonder that Stephen Hawking made the claim that "Philosophy is dead". Overlooking the fact that Hawking presents his own philosophy throughout his book, if premise 8 above is true, he's actually right- epistemology (a foundational branch of philosophy) is a fruitless and meaningless pursuit- thus by all intents and purposes, its dead. But in a logical twist of events, without knowledge science is dead, and any claim by Hawking that "God does not exist" or that "philosophy is dead" are relegated to mere opinion.
If one claims to know that God exists, they stand on solid epistemological ground. If one claims knowledge of anything, they are logically stuck with God's existence. If one claims that God does not exist, the phrase "I know God does not exist" is at best oxymoronic. If we claim to know anything, God is absolutely necessary; otherwise, we are deceiving ourselves and our only option would be to consider Krauss' Wager, but even that fails if Christianity is true.
Two recent sources that I recommend to further pursue this line of reasoning:
Alvin Plantinga- The Evolutionary Argument Against Naturalism (Outline, Video Lecture, and Debate)
Ronald Nash- The Word of God and the Mind of Man (the book and my review)
An ancient source that told us this nearly 2000 years ago AND predicted our refusal to accept it: Romans 1:18-23:
The wrath of God is being revealed from heaven against all the godlessness and wickedness of people, who suppress the truth by their wickedness, since what may be known about God is plain to them, because God has made it plain to them. For since the creation of the world God’s invisible qualities—his eternal power and divine nature—have been clearly seen, being understood from what has been made, so that people are without excuse. For although they knew God, they neither glorified him as God nor gave thanks to him, but their thinking became futile and their foolish hearts were darkened. Although they claimed to be wise, they became fools and exchanged the glory of the immortal God for images made to look like a mortal human being and birds and animals and reptiles.
More Great Posts on the Subject:
Wilkins and the EAAN- A Reply From Dr. Plantinga
Is Naturalism Rational?: The Self-Defeating Epistemology Behind Evolutionary Theories of Cognition