This is not to say the heart is only swirling emotion, mixed motives, and dark desire, without thought or reason. Far from it. According to Scripture, the heart is also where we do our deepest thinking. "Jesus, knowing what they were thinking in their hearts," is a common phrase in the Gospels. This might be most surprising for those who have accepted the Great Modern Mistake that "the mind equals reason and the heart equals emotion." Most people believe that. I heard it again, just last night, from a very astute and devoted young man. "The mind is our reason; the heart is emotion," he said. What popular nonsense. Solomon is remembered as the wisest man ever, and it was not because of the size of his brain. Rather, when God invited him to ask for anything in all the world, Solomon asked for a wise and discerning heart (1 Kings 3:9).
Our deepest thoughts are held in our hearts. Scripture itself claims to be "sharper than any double-edged sword, it penetrates even to dividing soul and spirit, joints and marrow; it judges the thoughts and attitudes of the heart" (Heb. 4:12). Not the feelings of the heart, the thoughts of the heart. Remember, when the shepherds reported the news that a company of angels had brought them out in the field, Mary "pondered them in her heart" (Luke 2:19), as you do when some news of great import keeps you up in the middle of the night. If you have a fear of heights, no amount of reasoning will get you to go bungee jumping. And if you are asked why you're paralyzed at the thought of it, you won't be able to explain. It is not rational, but it is your conviction nonetheless. Thus, the writer of Proverbs preempts Freud by about two thousand years when he says, "As [a man] thinketh in his heart, so is he" (Prov. 23:7 KJV). It is the thoughts and intents of the heart that shape a person's life.