Last night we had dinner with some college friends. He teaches at the local Christian college and his son and mine are roommates at our alma mater, Cedarville University, also a Christian college. Turns out that when I wasn't paying attention there was a bit of a flap at Cedarville and some profs were dismissed. These sorts of disputes are amusing only if you are far enough removed to see the irony.
I guess the dispute had something to do with "truth" and the university's position on truth. Truth is of particular interest to the Christian educator, since Christian Theistic interpretive frames are so radically different from secular interpretive frameworks. Adding to the irony, pursuant to a search through my class notes to review Advanced Calculus (in case my son asks me a poser I can't answer), I happened upon a blue book from the final exam in a course I took at Cedarville, "Man & Reliable Knowledge." Hmmm, I got an A on that exam, let's reread that essay, I thought. I hope Cedarville University hasn't forgotten what it taught me about truth in 1978.
If you are to dispute something, you must define your terms. I've used a two-fold definition of truth for several years: Ultimately, truth is what God knows. Proximately, truth is what corresponds to the state of the world. Simplistic I suppose, but it works for me.
Since I'm a Christian Theist, I tend to start with the ultimate: God. Truth is what God knows is a neat answer, but it is not immediately useful to someone who isn't God. Chirstian Theology teaches that God is transcendent and ineffable. No man will reach up into heaven and draw God down. Thus, if I am to have any idea what God knows, he'll have to reveal it to me. I believe there is a God and that this God has spoken. If you have a problem with that, OK, just don't call yourself a Christian. (You can't do Christianity without Christ.)
Not only do I believe God has spoken, but I agree with the consensus of Christian theology that teaches God has disclosed himself in General Revelation to all humanity, and Special Revelation to his people. More particularly, God reveals himself in Nature, Christ and the Bible. Again, if you have a problem with that, OK, just don't call yourself a Bible-believing Christian. Truth is transmitted from its ultimate source in God's mind to humanity through these three channels. If you aren't a Christian, you still have access to Truth (in spite of yourself) through Nature. And if you're not a Christian, you'll probably interpret Truth seen in Nature in a fashion consistent with your non-Christianity.
But if you are a Christian, and a Bible-believing Christian, you have two more channels through which you can tune into Truth: the Bible and Christ. Christians often engage in Bible-thumping, and Christians often claim to have a personal relationship with Christ. (And Christians often exhort non-Christians to establish a personal relationship with Christ, too.)
Now, IF, and I say IF, you buy into the paragraphs above, we can say some things about Truth through the contrapositive. Let's suppose you can't attain certainty. Narrowly speaking, that means you are uncertain of your relationship with Christ, or your understanding of the Bible, or your perception of Nature.
None of those things are bad in and of themselves. We should not take them for granted, and we should diligently question and distrust ourselves. We are fallen, finite beings and redemption is an incremental business.
(Healthy self-doubt is one thing, but denial is another thing. When the skeptic says, "there is no truth" or "noone can know anything for certain" there is little doubt in such a denial.)
There is another dimension of this matter: Exhaustive truth versus effective truth. God, being infinite understands exhaustively. I am not God and I am finite. In the last century Modernism suffered mortal wounds as it was proved that axiomatic systems (math) could not be consistent and complete (Goedel) and philosophy delved into various post-rational expressions. Modernism was naive in its expansive claims of truth and certainty. Post-modernism has rightly debunked this naivety.
However, many Post-moderns conflate debunking exhaustive knowledge with debunking ALL knowledge. A Post-modernist may be fully on board with his debunking of axiomatic systems, but he still uses arithmetic to balance his checkbook.
I like to say that Christian Theism is A-Modernist, neither Modernist nor Post-Modernist. We have to agree with the Post-modernist that we can't know everything, but disagree with him that we CAN KNOW SOMETHING. The Christian knows that the finite cannot encompass the infinite. If God reveals himself to mankind, he does so partially. The Bible says it "makes men wise unto salvation." Thus we should expect it to give us EFFECTIVE knowledge of God, but not EXHAUSTIVE knowledge.
Knowing that we won't have EXHAUSTIVE knowledge of God should motivate humility within us and an openness to those parts we don't yet know. But we can also rest in confident certainty of the bits of himself that God has EFFECTIVELY given us.