First of all, I do not intend to make this an anti-religion site, but a pro-reason one. Religion just happens to be what I am interested in at the moment, and it's a very popular subject. I am not trying to demonise it, but to study it objectively. Perhaps religion was a wrong choice, as it is a complex matter, and I should have started with something simpler, but there's no use crying over spilled milk now. In my next few posts, I will try to get everyone familiar with the "background" and make a case for certain assumptions that I use. Until then..
Usefulness of religion is debatable but irrelevant. I am interested in the truth, not usefulness. Sam Harris said in a debate once that it would be very useful to indoctrinate children with the idea that they have to study science or they will be devoured by a demon, yet no one is doing it. Indeed, the usefulness of religion is irrelevant to the religious folk as well. I've never heard anyone say that they believe something because it's useful. Usefulness only joins the argument when someone is trying to defend religion, claiming that it is responsible for certain good things too and that it provides answers to questions that (they think) no one else can answer. I disagree on both accounts. I can't think of a truly good thing that religion is responsible for, that did not cause more evil than good. As for the provision of certain answers, this is a bit complicated issue and I will deal with it in detail in some other post. For now, let's take a moment to bask in the words of Bertrand Russell, a man I greatly admire.
A common argument is that of morality i.e. that a good thing religion did is that it spread and/or invented morals. This argument is so lame that it should be ridiculed. On what grounds does one claim that the morality of their religion is superior to any other morality? Because a book says that something called God thinks it is superior? Assuming he exists, why should I think that he is right? How could God possibly convince me? Do you remember the Euthyphro dilemma? "Is what is morally good commanded by God because it is morally good, or is it morally good because it is commanded by God?" Think about that for a moment. Imagine standing in front of God and asking him "God, why should I accept your moral code?" and he answers either "Because I say so" or "Because it is the right thing to do". Without analysing whether or not these answers mean the same thing, I can say that they are both meaningless. I will address morality in detail at some later point, and further invalidate such arguments.
I did not say that the world would be at peace if it were void of religion nor am I so naive to believe it. Religion does not necessarily cause war. For example, it is quite reasonable to believe that the Crusades, or something equivalent, would have happened anyway, if it weren't for Christianity. However, religion is like a drug that makes soldiers more obedient and makes them do things they otherwise would not. When a leader wishes to wage a war people are more likely to support him if they believe that his word is God's word and you don't question God. We all know from experience that there are certain things only religious soldiers can do. Religion doesn't cause war, but it makes supersoldiers.