I have hardened his [Pharaoh's] heart ... in order to execute My miracles within him (Exodus 10:1).
Many commentaries raise the question: If God rendered Pharaoh unable to learn from experience, why did He then punish him for refusing to release the Israelites?
The answer lies in an under standing of free will. Many psychologists believe in "psychic determinism," that various circumstances can so affect people that they have no freedom of choice. People therefore act in certain ways because they must do so. Such concepts have been introduced in trials of those who have committed heinous crimes. So many lawyers have pleaded to the jury: "He was raised in such a terrible environment that he did not know better."
Torah rejects this idea. While many circumstances may impact upon a person, no human being with an intact brain is ever deprived of freedom of choice. We are always responsible for our actions. This concept is a pillar of the Torah's concept of human freedom.
The about-to-be-liberated Israelites were thus told: "I will indeed harden Pharaoh's heart and put great pressure upon him, but that will not deprive him of freedom of choice. Pharaoh will remain free and therefore will be held responsible for his behavior. In preparation for your liberation and ultimate acceptance of the Torah, you must retain this principle: people are always responsible for their actions."