One of the major innovations to psychological thought pioneered by this book was author Festinger's proposition of the theory of cognitive dissonance. This theory has been applied to modern groups and found to be amazingly accurate. Below is an excerpt from a site that used this book for its own evaluations of religious groups that wrongly predicted the return of Jesus.
"The authors comprised a research team who conducted a study of a small cult following of a Mrs. Marian Keech, a housewife who claimed to receive messages from aliens via automatic writing. The message of the aliens was one of a coming world cataclysm, but with the hope of surviving for the elect who listened to them through Keech and selected other mediums. What Festinger and his associates demonstrated in the end was that the failure of prophecy often has the opposite effect of what the average person might expect; the cult following often gets stronger and the members even more convinced of the truth of their actions and beliefs!
"Festinger observed that 'A man with a conviction is a hard man to change. Tell him you disagree and he turns away. Show him facts or figures and he questions your sources. Appeal to logic and he fails to see your point. We have all experienced the futility of trying to change a strong conviction, especially if the convinced person has some investment in his belief.'
"'We are familiar with the variety of ingenious defenses with which people protect their convictions, managing to keep them unscathed through the most devastating attacks. But man's resourcefulness goes beyond simply protecting a belief. Suppose an individual believes something with his whole heart; suppose further that he has a commitment to this belief, that he has taken irrevocable actions because of it; finally, suppose that he is presented with evidence, unequivocal and undeniable evidence, that his belief is wrong: what will happen? The individual will frequently emerge, not only unshaken, but even more convinced of the truth of his beliefs than ever before. Indeed, he may even show a new fervor about convincing and converting other people to his view.'
"When Prophecy Fails focuses on the failure of prophecies to come true, termed disconfirmation by Festinger, and the accompanied renewal of energy and faith in their source of divine guidance. His theory presupposes the cult having certain identifying features, such as: (a) belief held with deep conviction along with respective actions taken, (b) the belief or prediction must be specific enough to be disconfirmed (i.e., it didn't happen), (c) the believer is a member of a group of like-minded believers who support one another and even proselytize. All of these characteristics were present in the saucer cult.
"Of particular interest in Festinger's book is how the followers of Mrs. Keech reacted to each disconfirmation (failed date). Little attempt was made to deny the failure. The strength to continue in the movement was derived, not largely from the rationalizations , but from the very energy of the group itself and its dedication to the cause. This explains why proselytizing was so successful later in reinforcing the group's sagging belief system. Festinger relates:
"But whatever explanation is made, it is still by itself not sufficient. The dissonance is too important and though they may try to hide it, even from themselves, the believers still know that the prediction was false and all their preparations were in vain. The dissonance cannot be eliminated completely by denying or rationalizing the disconfirmation. But there is a way in which the remaining dissonance can be reduced. If more and more people can be persuaded that the system of belief is correct, then clearly it must, after all, be correct. Consider the extreme case: if everyone in the whole world believed something there would be no question at all as to the validity of this belief. It is for this reason that we observe the increase in proselytizing following disconfirmation. If the proselytizing proves successful, then by gathering more adherents and effectively surrounding himself with supporters, the believer reduces dissonance to the point where he can live with it.
"In the end, the members of the flying saucer cult did not give up their faith in the Guardians from outer space with their promises of a new world. Despite numerous prophecies and the resultant disappointment accentuated by many personal sacrifices, the group remained strong."