Dr. Stanley Aronson, dean of medicine emeritus at Brown University, points out that the world changes; that we don't know everything; and therefore all beliefs must be open to reexamination, so that we can determine which ones remain serviceable:
[In a purely-imaginary idyllic world, b]eliefs are determined solely by consensus, by common sense and the evidence provided by one’s immediate senses. It is universally believed in this serene world that the sun rotates around the earth, that the major religious texts are inerrant, that professional athletes employ steroids only for post-retirement arthritis and that the moon is composed of Camembert cheese. ... [In this world, e]motional peace becomes more important than anxiety or the corrosive knowledge of how little is known. Skepticism and curiosity become alien emotions.
The future, in such a pacific environment, would never be feared since the world will remain unchanged. Tomorrow, and all of the days that follow will be the same blissful Eden as yesterday or today. Ugliness, discord, contentiousness — and heresy — would remain as alien experiences confined to story books. And only the looming shadow of utter boredom would threaten this prospect of tranquility.
But imagine now, in this placid community, some rebellious individual, someone with the temerity to question the accepted beliefs of the majority, a person eager to assert that the ultimate enemy is not discord but ingrained bigotry and willful ignorance. The elders of this hypothetical community might initially condemn such a heretic, perhaps even destroy his spirit, but in their hearts they will know that all things but death change; that all beliefs must be tested continuously to determine which are false and which worthy and that it is the occasional heretic — with his provoking postulates — and not the peace-lover who brings progress and understanding to the community.