Was God unjust to harden Pharaoh’s heart?

[I find these Jewish answers to resonate with similar answers in Jonathan Edwards’s writings.]

The first to raise this question was the talmudic sage, Rabbi Yohanan, who observed that “this verse offers an excuse to heretics to argue that God denied them the opportunity to repent.” His colleague (and intellectual sparring partner), Reish Lakish, responded by observing that only after Pharaoh had established a pattern of obstinacy by hardening his own heart five times does God then proactively cause it to remain hardened.

http://www.jewishideasdaily.com/content/detail/continue-reading-pharaoh-and-macbeth