“Hardness of heart” is an expression of the pre-condition that a person is already in. They are in that state…with a closed mind and an uncompromising attitude.
God of course can give them thoughts leaning them to that state while subduing the opposite thoughts. As a matter of fact, we too can do that to another person by telling them some information while leaving out other information. The devil too is apt to do this very thing to lead us into sin, while our angel can prompt us to other good thoughts as well. This is the power any spirit has toward another spirit…to persuade and to lead by presentation of this or that idea.
“Hardness of Heart” is connected to pride in that the mind refuses to listen to any other idea and has no chance of softening. So my understanding is that when God heardens a persons’s heart, it simply means he does not send that person the aid to change his mind. Since the person has gotten himself in this condition in the first place without counsel from God, then there is no obligation on God’s part to change him, and in fact he would refuse help, and God would certainly would not force them to accept it.
This is what Jesus accused the Pharasees of doing, being hard. And He said that harlots and tax collectors had a better chance at heaven than they. They refused him time after time.
On the other hand “hardness of heart” can be quite good if it means that a person is stubborn in his love of God and will not forego it for any reason…Mary Magdelane. This too is a kind of hardness that forms in loving God with one’s whole heart, mind, and soul, over time. This happens when one uses God’s graces, and the other “hardness” happens when one throws away graces.
May God’s light shine thru you.