Despite Moses and Aaron’s signs and wonders, Pharaoh repeatedly “hardens his heart” and refuses to release his Israelite slaves.

What does it mean to “harden one’s heart” and why does the Torah first say that Pharaoh hardened his own heart and later say that God hardened Pharaoh’s heart?

A close reading of the text shows how those in power may rationalize their decisions—even disastrous decisions—in order to avoid acknowledging past mistakes. Pharaoh compounds his initial mistakes by becoming further entrenched in his determination not to let the slaves go free.

There is an important lesson in how mindsets become prisons. This phenomenon is called “confirmation bias”: when presented with a diversity of information, we selectively filter out anything that does not corroborate past experience.

In Pharaoh’s case, this is made much easier by the fact that Aaron and Moses start out with easily replicated tricks. Once assured that his own magicians can reproduce their “signs and wonders”, Pharaoh has no reason to see that anything unusual is afoot. The challenge to the status quo can be reasoned away.

Even when things escalate to a plague of lice, which Pharaoh’s court wizards are unable to reproduce, Pharaoh continues to “strengthen his heart.” Habits of thought are hard to break. Only when a plague strikes which the court wizards not only can’t reproduce, but from which they can’t even save themselves, does the text say, “God strengthened Pharaoh’s heart.”

Pharaoh’s problem is well-known to psychologists. Once a way of thinking becomes habituated, each time we resist change, we further lose our ability to see contradictory facts. Pharaoh’s dismissal of the evidence at hand was at first a conscious act, but by this point, it’s out of his hands; he has become a slave of his own “concept” and can no longer see what is obvious to everyone else.

And of course, what happened to Pharaoh in the realm of the mind had happened to Egyptian society in a more concrete sense. They had institutionalized slavery. It had become a habit, a permanent feature of their economy, which they could not leave behind of their own free will. The hardening of Pharaoh’s heart is a sign that what happens next is a miracle. It is a lesson in seeing God in the improbable and seemingly impossible.

Yael Shahar divides her time between researching trends in terrorism and learning Talmud.