Charles Hodge (1797-1878), American Presbyterian theologian of Princeton Seminary:
"A beautiful object in nature or art may be duly apprehended as an object of vision by an uncultivated man, who has no perception of its aesthetic excellence, and no corresponding feeling of delight in its contemplation. So it is with the unrenewed man. He may have an intellectual knowledge of the facts and doctrines of the Bible, but no spiritual discernment of their excellence, and no delight in them. . . .
"Out of the heart proceed all conscious, voluntary, moral exercises. A change of heart, therefore, is a change which precedes these exercises and determines their character. A new heart is to a man what goodness is to the tree in the parable of our Lord.
"In regeneration, therefore, there is a new life communicated to the soul; the man is the subject of a new birth; he receives a new nature or new heart, and becomes a new creature. As the change is neither in the substance nor in the mere exercises of the soul, it is in those immanent dispositions, principles, tastes, or habits which underlie all conscious exercises, and determine the character of the man and of all his acts."
--Systematic Theology (Grand Rapids: Eerdmans, 1946), 3:33, 35.