Blaise Pascal, the French philosopher, had a simple simple reason to believe in God. It's not as complex and bizarre as the Ontological Argument, nor is it as ridiculous as the argument from religious experience. Nevertheless, it seems to have two innate flaws.
His argument, more commonly known as his wager, goes like this:
You believe in God.
1) If God exists, you go to
heaven: your gain is infinite.
2) If God does not exist, your loss (the investment in your mistaken belief) is finite and therefore negligible.
You do not believe in God.3) If God exists, you go to
hell: your loss is infinite and your gain is zero.
4) If God does not exist, your gain is finite and therefore negligible.
Therefore, it is better to believe in God.
The two problems are:
FIRST: Most notably, this is in direct violation of the nature of Christianity. It seems as though believing in the All Mighty based on the statistical probabilities of being right or wrong, isn't exactly what the God of The Holy Bible had in mind. Also, on the note of making a wager, we can note Bertrand Russell's argument that even if there is just one religion that has it all right, just observing the vast number of religious institutions should, statistically speaking, lead one to wager that his belief is destined for damnation. (I guess that statistics class I took was good for something.)
SECOND: Premise number two has a biased and narrow point of view thus proving it fallacious. The problem is that if you choose to believe in God and He proves not to exist, your loss may be finite, but the loss of others may be infinite. Pascal infers that a belief will effect none but the believer. Religion has proven through thousands of years of history that an individual's belief is more than enough to cause the death of thousands. Before Christianity came about, pagan religions warred amongst one another; Christianity is responsible for the mass slaughter of Jews, Muslims, and other factions of its own faith such as Lutheran, Protestant, or Calvinist; and now more than ever we see Islam warring against Christianity, Judaism, and against differing factions within its own system of belief. Moreover, a belief in God has a certain political sway that can hinder sociological and scientific progression. Consequently, if one is to believe in God and He proves not to exist, the loss may indeed become infinite.