In 1954, psychologist Leon Festinger read a story in his local newspaper headlined “Prophecy from planet Clarion call to city: flee that flood.” The prophecy emanated from Chicago housewife Dorothy Martin, who, through an experiment with automatic writing, received a warning that the earth would be destroyed by a flood in the pre-dawn hours of 21 December 1954. The only hope of rescue was for those who believed the prophecy to prepare for deliverance by an alien spacecraft at midnight that day. Martin and her small band of followers left jobs, college, and spouses, and gave away money and possessions in preparation for the alien deliverance.

Fascinated by the story, Festinger and a handful of colleagues successfully infiltrated the group and began to study its social dynamics from the inside. On the eve of destruction, the group gathered together in a room, discarding all metallic objects from their persons. As midnight drew near, excitement mounted, but when a clock in the room showed 00:05, confused followers began murmuring. Someone noticed that a clock  on the other side of the room read 23:55, and so the group agreed the first must be wrong. When the visitors failed to show by 00:10, the group sat in stunned silence. By 04:00, Martin began to weep openly, but at 04:45, she received another message from God by divine writing: The faithfulness of the small group had caused him to change his mind so that the cataclysm was averted. In Festinger’s words, “The little group, sitting all night long, had spread so much light that God had saved the world from destruction.”

Festinger, who never believed the prophecy to begin with, wanted to study the psychology of the believers after the failed prophecy. What he found was that, rather than being disillusioned, the followers found a way to explain the failed prophecy. They simply would not admit that they had been wrong.

Festinger noted that this tendency is common to humankind. He coined the phrase “cognitive dissonance” and noted that, in the face of unfulfilled expectations, humans have a remarkable tendency to rationalise things. They do this in several ways.

One strategy is to deny the evidence that points contrary to belief. A smoker, for example, might rationalise his behaviour by completely denying all medical evidence that smoking is harmful to the body. A second strategy is to discredit the messenger. The smoker may attempt to discredit any medical professional who presents evidence, even to the point of finding contrary, though suspect, evidence to confirm his bias. A third strategy is to isolate oneself from the evidence, or to alienate the bearer of the evidence. The smoker might cut himself off from all exposure to the evidence, or, if it in in his power, somehow exile those who present evidence contrary to what he believes. In all of this, the smoker’s (misguided) certainty is dangerous.

Festinger is well-known for his studies in cognitive dissonance, but the patterns he observed are nothing new. The kind of dangerous certainty he studied is as old as the ages, as I was reminded recently in the record of John 9, where Jesus healed a man born blind.

That account is filled with misguided certainty. The disciples were certain that the blind man or perhaps his parents, were sinfully responsible for his blindness (v. 1). Their certainty reflected what they had been taught. The Jewish religious leaders in the first century taught that physical disability was the direct result of sin. They were certain of it. To be confronted with a formerly blind man, now healed, rocked their theological presuppositions. And so they resorted to rationalising the events—in precisely the ways that Festinger observed.

First, they tried to deny all evidence that pointed contrary to their precious beliefs. While the man himself claimed to be formerly blind, “the Jews [i.e. the Jewish religious leaders] did not believe that he had been blind and had received his sight” (v. 18). They even tried to confirm their belief by calling his parents, but that backfired when they confirmed his story (vv. 19–20).

Second, when they could not deny the evidence, they tried to discredit the messenger. They called the healed man and said, “Give glory to God. We know that this man is a sinner” (v. 24) Confronted with Jesus’ power, which proved his claims to authority, they tried to discredit him.

Third, when all else failed, they exiled the bearer of the evidence. After a long discussion, “they cast him out” (v. 34)—that is, they excommunicated him from the synagogue and, thereby, from Jewish religious life (cf. v. 22).

Simply put, the religious leaders had precious, long-held religious convictions, and they would not be swayed from their certainty. Rather than admitting the evidence, they resorted to every classic step to rationalise their misguided certainty. Their certainty became dangerous.

But not all certainty is dangerous. There is another evidence of certainty in this text, and it comes from the blind man: “Whether [Jesus] is a sinner I do not know. One thing I do know, that though I was blind, now I see.” He was certain that he had been blind but that, through Jesus, he could now see. But his certainty was safe, because it was rightly situated. He knew that he had met Jesus and that Jesus had changed his life.

So what is the difference between the dangerous certainty of the religious leaders and the safe certainty of the (formerly) blind man? It is simply this: The religious leaders’ certainty was in a system of belief—a philosophy, one might say—while the blind man’s certainty was in a person.

People today—even Christians—long for certainty. That is not necessarily a bad thing. Indeed, the Bible encourages us toward certainty—in some forms. John wrote his gospel “so that you may believe” (John 20:30–31). He wrote his first epistle “that you may know that you have eternal life” (1 John 5:13). (“Know” is the key word in 1 John.) Luke wrote his gospel “that you may have certainty concerning the things you have been taught” (Luke 1:1–4). But notice that, in each of these cases, the certainty that is aimed for is certainty about the person and work of Jesus Christ.

There is, of course, nothing inherently wrong with certainty or confidence. You would like to think, no doubt, that the doctor performing your surgery is confident in his ability to do what he is about to do. You would hope that your hairdresser is certain in her ability to style your hair as you have asked. Few things are more troublesome than an uncertain driver on a busy road.

But certainty can also be misplaced and misguided. Your surgeon may be quite confident in his abilities and yet find that he was not quite as skilled as he supposed. Your hairdresser’s certainty may leave you looking more early morning and less red carpet. Overconfident drivers cause accidents all the time.

When it comes to matters of eternal truth, the same is true. No one—except Jesus—was more certain in the first century religious world than the Pharisees. And yet they were dead wrong. They were, ultimately, the blind leading the blind—albeit quite certainly. Because their certainty was in a system rather than a person—because it was in their ideas about God rather than in God himself—it led people to destruction rather than to life. Their certainty was not in God, and not even in the Scriptures, but in their interpretation of the Scriptures.

As believers, we want to be certain, but we must pursue the right type of certainty—safe certainty rather than dangerous certainty. Truth, ultimately, is a person (John 14:6), and our certainty must be rooted in that person rather than our ideas about that person.

Skye Jethani captures well the important distinction between dangerous and safe certainty:

There is a difference between filling your head with knowledge and filling your life with the presence of Jesus. One makes us humble, and the other makes us prideful. The one makes us closed to other ideas and people, and the other opens us with graciousness and compassion to those who may disagree with us. One makes us a disciple of Jesus, and the other makes us blind Pharisees.

The New Testament, as we have seen, wants us to “have certainty concerning the things you have been taught,” but that certainty must be pursued, not by clinging tenaciously to a particular theological system, or a favourite Christian teacher, or a trusted confession of faith, but by placing our confidence fully and firmly in the Lord Jesus Christ. Only then will we be true disciples of Jesus rather than blind Pharisees.