Which God do you believe in? What or who is the object of your faith? Those are very important questions because the validity of faith is determined by its object.
Let us return to our airplane illustration. I can believe that planes fly from Washington to San Diego. I can even get on a plane that I believe is going to San Diego. However, if that plane is not going to San Diego, my faith is misguided.
A Harris Poll in 2013 found that 74% of US adults believe in God. That's down from 82% in previous years.
Robert Bella, in his book Habits of the Heart, quotes a woman whom he calls Sheila. Sheila says, "I believe in God. I can't remember the last time I went to church, but my faith has carried me a long way." This raises the question: does such a vague faith really make a difference in a person's life?
Then there are people like author Ayn Rand who once wrote, "I am done with the monster of we, the word of serfdom, of plunder, of misery, falsehood and shame. And now I see the free face of God and I raise this God over all the earth, this God who men have sought since men came into being, the God who will grant them joy and peace and pride. This God, this one word, I." Many people today believe in the God of self. They could confess the first four words of The Apostles' Creed: "I believe in God." But when they talk about God they are talking about themselves.
Shirley MacLaine once said, "Not that I am God, but that we are god, that all is god, that we're all part of a cosmic oneness. And if we don't feel that we're god, that's simply because we're ignorant. And the only way that we can banish our ignorance and discover our goodness is by enlightenment that will come through meditation." Shirley MacLaine could confess the first four words of The Apostles' Creed, but when she talks about God she is referring to this "cosmic oneness." For her and many others God is a force who is part of us all.
Distinct from these many different beliefs about God, Christians confess something unique when they say, "I believe in God the Father Almighty, maker of heaven and earth."
C. S. Lewis offers some helpful clarifications in Mere Christianity,
The first big division of humanity is into the majority, who believe in some kind of God or gods, and the minority who do not. On this point, Christianity lines up with the majority--lines up with ancient Greeks and Romans, modern savages, Stoics, Platonists, Hindus, Mohammedans, etc., against the modern Western European materialist.
Now I go on to the next big division. People who all believe in God can be divided according to the sort of God they believe in. There are two very different ideas on this subject. One of them is the idea that He is beyond good and evil. We humans call one thing good and another thing bad. But according to some people that is merely our human point of view. These people would say that the wiser you become the less you would want to call anything good or bad, and the more clearly you would see that everything is good in one way and bad in another, and that nothing could have been different. Consequently, these people think that long before you got anywhere near the divine point of view the distinction would have disappeared altogether. We call a cancer bad, they would say, because it kills a man; but you might just as well call a successful surgeon bad because he kills a cancer. It all depends on the point of view. The other and opposite idea is that God is quite definitely "good" or "righteous," a God who takes sides, who loves love and hates hatred, who wants us to behave in one way and not in another. The first of these views--the one that thinks God beyond good and evil--is called Pantheism. It was held by the great Prussian philosopher Hegel and, as far as I can understand them, by the Hindus. The other view is held by Jews, Mohammedans and Christians. (Mere Christianity, "The Rival Conceptions of God")