Apparently, I never posted on something very important I learned in Torah study several years ago.

For ancient Hebrews, the heart did not signify what we assume it does, reading it today. We assume the heart is what feels. But for them, the heart was not the seat of emotion. The soul — nephesh, the breath — was what feels emotions. The heart — levav — was the seat of understanding.

So when Pharaoh was said to be heard of heart, this did not mean he was unfeeling. It meant that he was unable to conceive things in any way except his. He had hardness of understanding, and this inability to understand made him unable to empathize.