Why do people do stupid things or embrace stupid ideas?

       Because they're stupid! 

       Not really. No one is always stupid and all of us, even the most intelligent, can be stupid occasionally. Actually, stupidity depends more upon the subject and the circumstances than upon the individual.

       Stupidities are activities or concepts adopted despite overwhelming and generally accepted contrary evidence. These frequently cause outcomes that are different (often disastrously) from the intended result. The definition does not include lapses of attention (accidents, et cetera), because judgment is not in play, or reasonable decisions based upon insufficient or inaccurate information. It does include creating situations that will certainly cause accidents; it also includes manufacturing nonsense evidence to support absurdity or hatred.

       Here are some examples:

• •A doomsday sect (Aum Shinri Kyo), believing it could hasten that day, released nerve gas into the Tokyo subway system. 
• •In California three-dozen people (from the Heaven's Gate cult) committed suicide believing they would join a spaceship lurking behind an approaching comet.
• •Too often we learn that a child has died because its parents chose prayer, and rejected medical treatment. In view of how often prayers by and for, even the most worthy, the most innocent and the most unfortunate are ignored, this is criminal stupidity even for those who believe in a merciful god.
• •The $27 million Creation Museum (near Petersburg, KY) was built to show that earth is only a few thousand years old, that its millions of species emerged fully formed and that humans and dinosaurs coexisted. However, it only shows the immense resources available for dissemination and defense of nonsense.

       While there is no evidence of common sense (sound judgment derived from evidence and experience) in such examples, the reasoning process is still intact. In each case the stupidity is logical in light of the underlying belief. 

      Pyramid schemes, televangelists, psychics, effortless weight loss, astrology, faith healing, alien abductions, zombification of cult members such as Branch Davidians and Moonies and of Limbaugh dittoheads, etcetera all flourish under the umbrella of belief.

      How about evil? If belief can impel people to monumental stupidity, can it also inspire people to monstrous brutality?

     Germans of the NAZI era were not intrinsically (genetically) evil. Nor were those Serbs who, more recently, inflicted such gruesome cruelty with such gusto in Bosnia and Kosovo. Nor are those jihadists whose fanaticism has destroyed more Muslims than hated infidels. For generations, in churches and mosques, in folklore and harangues, in classrooms and lecture halls, in print and broadcast media, those peoples were subjected to torrents of hatred and xenophobia, and to notions of their own superiority, virtue and victimhood. It is by such belief-infused loathing and paranoia, that normal people are made to bomb and torture and burn and kill.

       Communism was designed, and proselytized, in the belief that it was the way to improve the lives of the "masses". Despite famines due to its stupid agricultural policies, despite relocations of whole populations and purges including slaughter of millions perceived to be incompatible with communist ideology, that belief was widely held for many decades. It still exists among some people.

      From the Inquisition and crusades of Medieval Europe to the killing fields of Cambodia, Rwanda and Darfur, murders and massacres have been done in belief that the world could be improved by exterminating some part of humanity.

     “Spare the rod and spoil the child” is often used to rationalize child abuse. Inferiority of women, homophobia, holy war, ethnic and racial hatred are always justified by belief.

     However, there is a crucial difference. Unlike stupidity, evil requires no underlying belief; greed, lust and power-hunger are sufficient. But, when evil needs support, beliefs are readily adjusted:

• •Pedophiles often believe that children benefit when introduced to sex by an adult. Many men believe that many women, consciously or unconsciously, desire rape. Some even manage to believe that sex with a virgin could cure their venereal disease (for example syphilis and gonorrhea in Victorian England, AIDS today's Far East). 
• •Slave owners -- in antebellum US and elsewhere -- often convince themselves that their slaves are better off in servitude.
• •The Conquistadors justified their exploitation and brutalization of native peoples by "bringing Christ to the heathens and saving souls".
• •In the United States, the "opening of the West" was not just simple folk seeking a better life; it was also greed, and resulted in a century of duplicity, exploitation and murder. We called it "manifest destiny". We said, "The only good Indian is a dead Indian". So we believed, and so we justified the ethnic cleansing of America.

      We believe for many reasons: tradition, convenience, discontent, desperation; and belief enables hope. Many beliefs are benign, even beneficial. But before a belief is accepted it should be examined in light of real evidence, empathy and the Golden Rule. This is essential because beliefs are too easily controlled by clever instigators, extremists and militants who tap into dreams and fears. "Evidence" is invented as needed. "Truth" flows from the mouths of leaders into the brains of followers. We are exhorted to purge doubt, purify thought, intensify faith. For those who want to believe, nothing is too absurd! Fanaticism, foolishness and inhumanity increase without limit; common sense and understanding are abandoned.

      So, when we’re stupid and often when we’re evil, it’s not because we cannot reason or because we cannot apprehend the damage and misery that we may be inflicting; it’s because of what we believe. Unexamined belief is the instrument by which demagogues, charlatans and holy men manipulate our minds and our lives. Clearly, to have a world with less stupidity and less evil, we need more critical thinking and healthy skepticism, less gullibility, less faith.