The Pharaohs were considered Gods by the Egyptians. The Pharaoh at the time of Moses was considered to be the incarnation of Horus the successor of Osiris. He was given the titles of "Sun of the Two Worlds", "Mighty God", "Offspring of Ra", "The Eternal", amongst a few. His crown actually displayed the image of a cobra., and pharaoh's image was placed in temples alongside the other gods. As god, his word was law and he ruled not according to a law code but by decree. It would therefore appear that this man was not a reasonable man, he had a lot to lose by letting the Hebrew slaves go so therefore, whether God hardened his heart or not, there is every likelihood that no way would he let the Hebrews leave.