The unexamined faith is not worth having. Religion has had many critics from without, and still does. But one characteristic feature of the Biblical tradition is that it is full of critics from within, those who examine their own tradition and challenge themselves first, and then their contemporaries, to rethink it and to live it differently.
There are those who would like to avoid such critical introspection and self-examination, perhaps at all costs. “Leave us alone”, they might say, “we’re happy as we are.” But just as one might believe oneself happy living in ignorance of one’s wife’s affair, for example, it can also be argued that the “happiness” in such cases is illusory. One’s alleged happiness is maintained at the cost of a failing marriage and a decaying relationship infested with deceit. And presumably, were the wife happy and the relationship healthy, the affair would not be occuring. And so in such cases one is in fact valuing one’s own deluded happiness over the happiness and well-being of others.