““Whoever is not with me is against me, and whoever does not gather with me scatters.” (Matthew 12:30)
When it comes to ultimate things, no one is really neutral —particularly when the ultimate thing in question is God. In fact, the Bible says human beings are deeply and profoundly hostile to God (Rom 1:18-23; 8:7; Col 1:21). This is important, because, when you discuss your faith with unbelievers, they will often ask you to lay aside your faith commitment to Jesus Christ in order to meet them on some supposedly neutral common ground, like human reason, or scientific evidence. Don’t make this mistake. The ground they suggest is not neutral. It's actually their home turf. They are leading you into a trap from which there is no good way out. As Bonhoeffer famously once said, “If you board the wrong train, it is no use running along the corridor in the other direction.”
Let me see if I can flesh that out a little. To give up your distinctly Christian way of thinking is to surrender the foundation of all knowledge, to give up your faith, to betray your Savior, and to baptize unbelief, doubt, and epistemological rebellion with an air of credibility.
Okay, I know its early, too early for words like Epistemological -- which really means: Your way of thinking about everything-- So epistemological rebellion is just a fancy way of saying that the deepest problem unregenerate human beings face is that they/we refuse to see the world from God’s perspective. Instead of listening, we speak, and insist on defining reality on our own terms and for our own pleasure.
Okay, I know it's too early for that explanation as well. You win! You go grab some coffee, and I'll try a story. Let's say there is a student out there in a North Carolinian school who hates English, and what's more he hates his English teacher to boot. One day he attends class, folds his arms, and says, "I am not taking my final exam. I don't believe in words!"
This is clearly a problem. How should the teacher respond? Pull out a dictionary and say, "Words? What do you mean you don't believe in words? Look, son, here's millions of them!"? Of course, not. The student really does believe in words. That's not his real problem. He just did, after all, use words to say he didn't believe in them! He's clearly crazy, hateful, or both.
Well it is exactly like that with the Atheist? He doesn't believe in God, but he does believe in certainty, truth, logic, knowledge, morality, justice, goodness, beauty, and wisdom. The problem is: how do you get any of these things without God. Where do you get certainty without God, truth without God, knowledge without God, or Justice without God? And the list just goes on.
Without God, these concepts have no real meaning, they become mere human constructs, like table manners, or the taboo against nose-picking. It's actually worse than that: without God the human mind and all its profundity is but a soup of chemicals smoking and fizzing away randomly, mindlessly, purposelessly. Without God, there is no maker of the human mind. Without God there can be no ghost (no real human person or spirit) in the machine guiding the process of actually thinking. Why on earth would anyone trust such an irrational, fluke-ish contraption? Who would have thunk it?
No human being can live life on such a basis. But, again, just like our word hating student, who uses words to deny words, the Atheist betrays himself with certainty. Deep down we are all certain about knowledge, truth, logic, morality, justice, etc. We know these are realities tied into the very warp and the woof of our humanity. We can neither pretend indifference to these things, or live as if they were arbitrary, evolving customs.
From where do these certainties come? They comes from the only place from which they can come, from God. It's only as you start with God that you can have any knowledge about anything. Isn't that what Solomon meant, "The Fear of the Lord is the beginning of knowledge (about anything)"?
Let me illustrate: How do you know the sky is blue? Well because it looks blue to me, you might say. Okay, but how do you know your eyes aren't playing tricks on you, or that you aren't color blind? Well, you might say, I ask my friend and he says it looks blue to him as well. But how do you know you are both seeing the same color, or even the real color? How do you know the sky is even there in the first place, or, for that matter, that your friend even exists?
Now, you say, you are being silly! I would say, no, not if we suppose an atheistical universe. Without God, you see, none of these things can be taken for granted. No matter how hard you try, you can't see round your eyes to check your eyes! If you think about it, this problem smashes man's arrogant attempt to find certainty without God at absolutely every level of thought and life.
Some atheists are honest about this, and try to escape the very idea of certainty about anything. They will say things like, "There is no truth, no one can be certain, and I live in a world of I-don't-knows!" But even here there is certainty: because they "know" there is no truth, they are certain they can't be certain, and they seem to know they live in a world of I-don't-knows! As hard as it might be to believe, there is a limit to their ignorance. No man really can know nothing.
By contrast, the Christian starts with the certainty of God and from that all other certainties flow. God exists. He is true and never lies. He made all things, blue sky included. He made me in His image with powers to see and to interact with his creation. His Son also shares my humanity and lived on this world in my nature without sin. Therefore, I assume that what I see corresponds to reality. I see the world Jesus saw. In like manner, I can assume, that as His image bearer, I come hardwired to yearn for the good, the beautiful, and the true. I am certain of them because I am certain of God.
At this point the atheist might throw up his hands and say, okay maybe you are right, maybe the world is a chaotic and irrational mess, but on what basis do you have the right to bring God into the picture. How do you know such a God really exists, and that He is not just a nice idea you dream up to make the mess of life more comfortable? To which I reply, because God has revealed Himself to us, as you, my dear friend, know only too well. I try to be polite here, but God says, "Only a fool would believe otherwise!"
So when you talk to an unbeliever, do not grant him for the sake of argument that certainty is in doubt, or that folly might be wise, or that human reason might actually be the only way to know anything for sure, or that God must play by science's rules before science must believe in Him, or that God might in fact not exist, or that the truthfulness of His word might be open for debate. To flesh Bonhoeffer out a little, if you get on the atheist's train, you are going to the atheist's destination, no matter how fast you run down the aisle in the opposite direction!
Above all: speak this truth in love! Our job is to win people not arguments.