Throughout my life, I have questioned my Christian faith. On two occasions in my life, however, I have seriously considered the possibility that the God who has directed every aspect of my life is just a very nuanced invisible friend. The first time when I was 19 years old and took a college course on faith. The second time is right now.
The arguments against the existence of a deity are quite sound. Most faiths, including my own, are neither exemplars of morality nor of intellectual ideals. Important books like Richard Dawkins' "The God Delusion" and Sam Harris' "Letter to a Christian Nation" seek to destroy any reasonable basis for faith in the Christian God or any other god. Not to mention that a few years back, Socrates did a pretty good job at this as well.
