More than a matter of the mind

Jonathan Edwards on the importance of the heart and its affections:

I am bold to assert, that there never was any considerable change wrought in the mind or conversation of any person, by anything of a religious nature, that ever he read, hear, or saw, that had not his affection moved.  Never was a natural man engaged earnestly to seek his salvation; never were any such brought to cry after wisdom, and lift up their voice for understanding, and to wrestle with God in prayer for mercy; and never was one humbled, and brought to the foot of God, from anything that ever he heard or imagined of his own unworthiness and deserving of God's displeasure; nor was ever one induced to fly for refuge unto Christ, while his heart remained unaffected.  Nor was there ever a saint awakened out of a cold, lifeless flame, or recovered from a declining state in religion, and brought back from a lamentable departure from God, without have his heart affected.  And in a word, there was never anything considerable brought to pass in the heart or life of any man living, by the things of religion, that had not his heart deeply affected by those things.  

In other words:

...he that has doctrinal knowledge and speculation only, without affection, never is engaged in the business of religion. 

Also see Ezekiel 36:26.