Here are some great comments from Greg Koukl (Founder of Stand To Reason) on the four big questions:
All the big questions, —issues of origin, meaning, morality, and destiny—and all the secondary concerns, too—issues of sex, gender, liberty, equality, bodily rights, etc.—eventually come down to one. Are we our own, or do we belong to Someone else? If there is a God, then, to borrow from C.S. Lewis, we are the tenants and He is the Landlord. If there is no God, then all is clay and nothing but clay.
Thus, the God question is the first question whose answer lays the foundation for answers to all the others. That foundational question comes in two steps for modern people: Does God exist? If so, is He good? For Christianity to make sense in the face of the social pushback and the spirit of this age, both issues need to be addressed.
Let me offer you, in a nutshell, what I think is the easiest, most powerful way, strategically, to make your case for God. I have been using it a long time in a variety of ways, though it really came together for me quite by accident when my eldest daughter, then about eight years old, asked me an important question.
“Papa,” Annabeth asked, “how do we know God is true?” She was already a Christian, baptized at six, but was now trying to connect the dots, not regarding the “What?” but regarding the “Why?” “Why God?” was her question.
What do you say to a youngster who already believes in God but is not sure why belief in God is defensible? That was my challenge. And nothing technical would do, not at her age.
I thought for a moment how I could say something meaningful in a simple way. Then an idea crystallized in my mind. “Annabeth,” I said, “the reason we believe God is true is that God is the best explanation for the way things are.” The minute I said it I realized I had summed up in a single sentence a major thrust of how I had approached defending Christianity for decades.
You might call the principle the explanatory power of Christian theism; that is, the important details of the Christian worldview make good sense of what we actually discover the world to be like. It turns out that the picture of reality the Bible presents fits the world as we discover it and resonates with our deepest intuitions about origin, meaning, morality, and destiny.
Note the advantage to this “best explanation” strategy. There’s no need to dismissively deny the possibility of other options. We can give fair consideration to the alternatives. We’re not offering the only explanation, just the best one, all things considered.
Our confidence is based on a point I have made before: Reality is on our side. My point with Annabeth was that Christianity explains reality best, that the existence of God makes sense of features of the world that, without Him, would be unlikely in the extreme. Other worldview stories do not fare well by this standard because certain obvious features of the world simply do not fit into their narrative, putting them on a collision course with reality. So fix this fact first in your mind: God is the best explanation for the way things are.