According to Harold Camping - a charismatic engineer-turned-prophet leader of Family Radio - the world was supposed to end May 21, 2011. That was yesterday. It didn't happen.
I don't think that the people who left their families and jobs, or gave away their homes, or donated money by the millions to Camping were just pretending to believe the world would end. I think they really believed it would happen, and were genuinely surprised - even disappointed - when it did not.
Unreasonable beliefs are commonly found in religion, alternative medical practices (homeopathy), or psychic phenomenon (ESP, astrology, and psychic readings). Belief in God, despite any evidence of God, is nearly universal in the United States. However, belief in psi (or psychic phenomena) is also very common. According to a recent Pew Forum poll, 29% of Americans believe they have been in touch with the dead, 26% believe in spiritual energy, 25% believe in astrology, 24% believe in reincarnation, 30% believe in UFO's, while 46% believe in ESP.
To put all this prevalence of wackiness in perspective, consider that only 26% of Americans agree with Darwin that life evolved through natural selection - which is supported by mountains of accumulating and converging objective data gathered by scientists over the last 150 years - while 60% of Americans "believe that humans and other animals have either always existed in their present form or have evolved over time under the guidance of a Supreme Being" - which is supported by no evidence at all. Clearly, Americans (like most people) believe a lot of bullshit.
There are many reasons people believe in bullshit. However, one of the most common, persistent, and convincing to believers is this: I know X is true, because I feel X is true. It doesn't matter that there is no scientific evidence of X, it doesn't matter that they may not have ever experienced X with their five physical senses, it doesn't matter that there are serious scientific or philosophical arguments against X. None of it matters. If someone feels that X is real or true or right, then they will find a way to believe.
The unspecified problem of evidentialism (google it) is solved by reliabilism - which states that for a true belief to be justified (and therefore count as knowledge) that the belief is brought about through "reliable" mechanisms. Or in other words, a reliable mechanism is a mechanism that tends to produce true beliefs. A basic example would be our senses of sight and sound. These sense have evolved because they were pretty reliable in helping us avoid being eaten by predators or to catch prey ourselves (among other things). Nowadays vision and hearing are pretty reliable in helping us avoid getting hit by cars when we pull out of our neighborhood. Even though our senses are prone to hallucinations, they are fairly reliable.
The scientific method would be another reliable method of aquiring knowledge because it relies on observation of facts and data, makes testable hypothesis, and makes conclusions that can be falsified (proven wrong) and reproduced by anybody else. And like people driving in rush-hour traffic without constantly bumping into eachother, the scientific method relies on observations by many different people all making the same fairly reliable observations with the same fairly reliable tools: our senses.
So what about religious feelings? Do these count as a reliable mechanism to aquire knowledge? Alvin Plantinga, one of the greatest theologians of modern times, said that God has given every one of us a God-sensing faculty (or sensus divinitatus) that enables us to "know" God in a reliable way. According to Plantinga, God would obviously want everybody to know himself, so he gave everybody this sensus divinitatus (also sometimes called "the light of Christ" or "Holy Ghost" by Mormons). So how does Plantinga explain why not everybody has such unambiguous and reliable experiences of God manifest in their life? Sin, of course:
Were it not for sin and its effects, God's presence and glory would be as obvious and uncontroversial to us all as the presence of other minds, physical objects and the past. Like any cognitive process, however, the sensus divinitatis can malfunction; as a result of sin, it has been damaged.Even without this poppycock notion that anybody who doesn't know God is sinful, Plantinga's reliable God-sensor of knowledge has other problems. One of the problems with a sensus divinitatus (or Holy Ghost, or light of Christ - whatever you call it) being a reliable source of knowledge is that billions of other people have spiritual feelings that lead them to adopt mutually incompatible conclusions. Therefore it seems that relying on our religious feelings, despite what Plantinga says, is extremely unreliable.
Also problematic is the fact that spiritual feelings can by fabricated by hallucinogenic drugs, electrical stimulation of your brains temporal lobe, seizure activity in your temporal lobes, and generalized brain hypoxia - common in pilots pulling high G-force turns or patients while experiencing "near death experiences" when their heart does not pump enough blood to your brain.
Religious feelings can also be reproduced through meditation, rituals, prayer, isolation, architecture, collective chanting or singing, and fasting - which is the stuff of religion. It's no wonder why religions all have these elements in their worship.
Religious feelings also tend to be culturally specific. For example, people living in predominantly Christian countries experience Jesus or Mary, while people living just across the border in predominantly Muslim counties do not. And within these countries, religious experiences are influenced by the different cultural expectations of the various branches of Christianity or Islam. For example, Mormons will have religious experiences that reinforce their brand of religion, while Pentecostals living down the street will have religious experiences that reinforce theirs. This should make one wonder if the religious feelings and experiences they are having are more related to geography and cultural expectations than anything else (ie. that the experiences correlate with the truth).
And finally, these religious experiences are mutually exclusive and contradictory. Analyzing all the different religious revelations and personal experiences, throughout the course of history, produces a hodge-podge of contradictory claims. They can't all be right, and it's unlikely that any of them are.
So now, let me say something nice. I don't think that people who have religious feelings are making them up. I think religious claimants (even the nuttiest of them like Harold Camping and his followers) are sincere people who genuinely believe what they preach. I just wish that they would be a little more humble and private in their views. I wish they were willing to consider that believing something really strongly, because they feel it really strongly, does not mean they know anything. Maybe they should just say "I believe" instead of "I know!" Doesn't religious faith imply a lack of knowledge - as well as admit a certain level of doubt?