Survivorship Bias

Francis Bacon, often crdited with the principle that beliefs must be grouded in observation, wrote of a man who was taken to a house of worship and shown a painting of sailors who had escaped shipwreck by paying thier holy vows. The man was asked whether this didn't prove the power of the gods. "Aye," he answered, "but where are they painted that were drowned after their vows?"

Steven Pinker, The Better Angels of Our Nature, p. 144

Keep Your Identity Robust

A broader danger of unverifiable beliefs is the temptation to defend them by violent means. People become wedded to their beliefs, because the validity of those beliefs reflects on their competence, commends them as authorities, and rationalizes their mandate to lead. Challenge a person's beliefs, and you challenge his dignity, standing, and power. And when those beliefs are based on nothing but faith, they are chronically fragile. [...] Since one cannot defend a belief based on faith by persuading skeptics it is true, the faithful are apt to react to unbelief with rage, and may try to eliminate that affront to everything that makes their lives meaningful.

Steven Pinker, The Better Angels of our Nature, p. 140

The Scientific Method in Action

Some officials became infected with the scientific spirit and tested the witchcraft hypothesis for themselves. A Milanese judge killed his mule, accused his servant of committing the misdeed, and had him subjected to torture, whereupon the man confessed to the crime; he even refused to recant on the gallows for fear of being tortured again. (today this experiment would not be approved  by committees for the protection of human subjects in research.) The judge then abolished the use of torture in his court.

Steven Pinker, The Better Angels of our Nature, p. 140