Physicist Richard Feynman observed that the methods of science help us distinguish real truth from what we only want to be true: "The first principle is that you must not fool yourself, and you are the easiest person to fool."
Science can, of course, be wrong. Continental drift, for example, was laughed off for years. But in the end the method is justified by its success. Without science, we'd all live short, miserable and disease-ridden lives, without the amenities of medicine or technology. As Stephen Hawking proclaimed, science wins because it works.
Does religion work? It brings some of us solace, impels some to do good (and others to fly planes into buildings), and buttresses the same moral truths embraced by atheists, but does it help us better understand our world or our universe? Hardly. Note that almost all religions make specific claims about the world involving matters such as the existence of miracles, answered prayers wonder-working saints and divine cures, virgin births, annunciations and resurrections. These factual claims, whose truth is a bedrock of belief, bring religion within the realm of scientific study. But rather than relying on reason and evidence to support them, faith relies on revelation, dogma and authority. Hebrews 11:1 states, with complete accuracy, "Now faith is the substance of things hoped for, the conviction of things not seen." Indeed, a doubting-Thomas demand for evidence is often considered rude.
And this leads to the biggest problem with religious "truth": There's no way of knowing whether it's true. I've never met a Christian, for instance, who has been able to tell me what observations about the universe would make him abandon his beliefs in God and Jesus. (I would have thought that the Holocaust could do it, but apparently not.) There is no horror, no amount of evil in the world, that a true believer can't rationalize as consistent with a loving God. It's the ultimate way of fooling yourself. But how can you be sure you're right if you can't tell whether you're wrong?
The religious approach to understanding inevitably results in different faiths holding incompatible "truths" about the world. Many Christians believe that if you don't accept Jesus as savior, you'll burn in hell for eternity. Muslims hold the exact opposite: Those who see Jesus as God's son are the ones who will roast. Some Jews see Jesus as a prophet, but not the messiah. Which belief, if any, is right? Because there's no way to decide, religions have duked it out for centuries, spawning humanity's miserable history of religious warfare and persecution.
In contrast, scientists don't kill each other over matters such as continental drift. We have better ways to settle our differences. There is no Catholic science, no Hindu science, no Muslim science — just science, a multicultural search for truth. The difference between science and faith, then, can be summed up simply: In religion faith is a virtue; in science it's a vice.