What use, we sometimes wonder, are arguments? People are rarely persuaded by them to accept something they're not already disposed to believe so why bother? People who disbelieve in God, for example, don't often change their mind because they've heard someone effectively argue the opposite position.
This is probably because disbelief is not usually a consequence of a lack of proof in, or evidence for, God's existence. More often it's due to either a bad experience with Christians or the church, an incredulity over the doctrine of Christian exclusivism, the prevalence of suffering and terror in the world, or a simple desire that Christianity not be true and that God not exist. As such it's not something that can be changed by appeals to a person's reason.
For most people, believers and unbelievers alike, faith is a matter of the heart, not the head. It's rarely arrived at, or decided upon, on rational grounds. People are drawn to faith through their hearts or they reject it because their hearts are closed to it. People are moved more by story, song, film, testimonial, and what they see in other people's lives than they are, say, by Anselm's ontological argument.
For a man to be convinced of an idea or a truth, his heart needs to be persuaded, and, it's important to note, the head will always follow the heart. But arguments are useless with the heart, they only appeal to the head. Since the heart is the gate to the head, if the heart is closed no argument will ever compel the head to accept it. On the other hand, if the heart is sold on an idea anyway, then arguments aren't necessary. In most human beings the heart is the master. The head is merely an advisor that submits to the will of the heart.
Thus arguments aren't of much use to people who are unwilling to accept the conclusion that God is real. A person who doesn't want a particular idea to be true, whose heart is closed to it, will not be persuaded no matter how compelling the argument. He'll always find some way to evade its force and reject the idea.
Yet arguments are not without value. Arguments can strengthen the faith of those who already believe and they can blow away intellectual smokescreens that skepticism often hides behind. Most importantly, perhaps, they can alter the intellectual ambiance of a culture so that the assumption that Christianity is intellectually disreputable is no longer prevalent among young people. Arguments can shape the culture so that whether people accept their conclusions or not they live and move in an environment in which they know that belief can no longer be credibly portrayed as irrational. Indeed, arguments can so influence the larger culture that people accept that belief is even the most rational option, even if they don't always submit to the realization.
There are good reasons to believe that God exists and that Christianity is true, but the person who doesn't want to accept those beliefs, whose heart is already dead set against them, will, like a man who can look at the sky at noon on a clear day and claim not to see the sun, fail to see those reasons.
Even so, most people who have watched the debates between William Lane Craig and Christopher Hitchens or have read the work of any number of Christian philosophers and apologists will, whatever conclusions they eventually draw for their own lives, have a very difficult time holding on to the notion that being a theist is somehow for fools, dunces, and old people.
RLC
