Exodus 7:13

And He hardened Pharaoh's heart, that he hearkened not unto them; as the Lord had said. The fact that his wise men with their witchcraft succeeded in imitating the miracle of Aaron was enough to decide Pharaoh against the Lord, the result being a hardening of his heart. Even so many an unbeliever in our days is confirmed in his opposition to the Gospel by the claims advanced by a false science.