To be born again means that God has given each of us a new heart. Just as every function and aspect of our old heart was perilously infected by sin, so also nothing in our new heart remains untouched by God’s grace—including our mind. God has graciously enlightened our understanding. Now we see our sin and we see its remedy in Christ so that we might call on the Lord with “a pure heart” (2 Tim. 2:22). God’s grace and truth shine “in our hearts to give the light of the knowledge of the glory of God in the face of Jesus Christ” (2 Cor. 4:6). This light does not bypass the mind. It opens the mind. 

Life is filled with choices. Some are as mundane as paper or plastic, while others are more serious, like the friend who insists, “You’re either with me or against me.” We are told that we must choose between success or happiness, hard work or a social life, science or art, being an extrovert or an introvert. It’s this or that. Some Christians would add that you must choose between your head and your heart. It reminds me of the Tin Man in The Wonderful Wizard of Oz who said to the Scarecrow, “But once I had brains, and a heart also; so, having tried them both, I should much rather have a heart.” The Tin Man apparently considered the head and the heart irreconcilable rivals. Perhaps you agree.

We moderns tend to associate the heart with feeling, not thinking. Naturally, this leads some to think that our knowledge of God and our love for God are two separate things. Or that it’s more spiritual to draw insight from inward intuition than theological reflection. Must a Christian, then, choose between a religion of the intellect and of the affections?

The Bible never asks us to choose between our heart and our thinking. It never encourages the impression that the heart’s mind is somehow less spiritual than the heart’s desires or will. The Bible holds these together, cordially. It might surprise many Christians to hear that according to Scripture, if your heart principally does one thing: it thinks. Let’s explore how Scripture regards the heart and its functions.

The Heart’s Unity and Its Complexity

The Bible uses the word heart more than any other word to describe our inner person (far more than words like soul and spirit). Summarizing the teaching of Scripture, we can say the heart governs the totality of our inner self—everything we think, desire, and choose flows from this one source. It is the fountainhead of every spiritual faculty within us—the spring of every motive, the seat of every passion, and the center of every thought. Your heart is the helm of your ship. The bearing it sets is the course your life will follow. That’s why the Bible interconnects your speech, repentance, faith, service, treasure, obedience, worship, walk, and love with “all your heart.” Put simply, the Bible speaks of your capacity to think, desire, feel, and choose as centered in your heart.

Within this central unity of the heart, however, the Bible also describes a threefold complexity of functions: the mind, the desires, and the will. To put this another way, the heart includes what we know (our intellect, knowledge, thought, intentions, ideas, meditation, memory, imagination), what we love (what we desire, want, seek, crave, yearn for, feel), and what we choose (whether we will resist or submit, whether we will say “yes” or “no”).

The biblical language of the heart, therefore, beautifully brings together this cooperative network of our intellect, affections, and will. This complex unity of the heart has been foundational to my own Reformed theological tradition in both its scholarly and popular forms. As a consistent biblical paradigm, it has also proven itself over time and has been confirmed by contemporary scholarship. Thus the word heart in Scripture is simple enough to reflect our inner unity and comprehensive enough to capture our inner threefold complexity.

The Heart’s Desires

Whether pursued righteously or sinfully, the heart desires companionship, security, encouragement, happiness, comfort, and satisfaction. The word used throughout the Bible for lust, fleshly passion, and worldly desire is the same word Jesus uses to express his desire to eat the Passover with his disciples. The term Paul uses for the desires of the flesh is the same one he uses for the desires of the Spirit (Gal. 5:16–17). Desires become sinful only when their object is out of bounds or the desire itself is out of balance. But all desires are strong cravings—hungry and thirsty spiritual appetites. We desire not simply what we like but what we love—what Christ calls our treasure (Matt. 6:21). We get emotional about our treasure. That is why Scripture associates the heart with feelings like anger, joy, envy, rage, anxiety, longing, sorrow, lovesickness, anguish, despair, and many other emotions (depending on whether our desires are satisfied, frustrated, or denied). Our hearts go out to what we love, and in this way our desires bring out what lies at the core of who we are.

The Heart’s Will

Often when the word heart appears in Scripture, its volitional function is in view: not only what we want but what we choose. The will decides whether we resist or submit to what we desire. Will my heart say yes or no? The battle for control of the heart is fought in the will. Which way the battle goes corresponds with the will’s strength or weakness, its callousness or brokenness, its being hardened by sin or made new by grace. The unbelieving heart’s sinful will is a stubborn, unyielding “heart of stone”—like Pharaoh’s hardened heart that resists God in rebellion. At the same time, this will is weak, unable to resist temptation. It is enslaved, unstable, apathetic, and afraid. The Christian’s heart made new by the Spirit, in direct contrast, enjoys a will that is both surrendered and strengthened. While always imperfect in this life, it nevertheless increasingly bows before God, grieves over sin, and serves Christ with humility. That same renewed heart has resolved to obey the Lord and is emboldened to die to sin, defy the world, and resist the devil. Your heart does not simply know or desire; it decides.

The Heart’s Mind

Finally, according to the Bible, the third function or capacity of the heart is to think. Let’s spend a little more time on this one, since we’re so used to thinking about thinking with our heads. You will not find biblical references to your head as the locale for your thinking.

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