For centuries, human nature was viewed through the loves, desires, and affections of the heart. It was the core of our innermost being, inseparable from the soul.

Through nearly 1,000 verses in the Old and New Testaments, God’s word reveals the heart as the command center of the person. Christian theologians and many ancient philosophers understood this: the intellect does not govern human behavior; our loves, desires, and will profoundly shape what we choose and how we live.

The word “psychology” literally means the study (logos) of the soul or inner life (psyche). Why, then, does modern psychology fixate on the mind?

The Heart as the Source

In our fallen world, we yearn to make sense out of chaos. We seek to understand the motivations that guide us. Modern psychology tells us our mental processes reveal deeper truths about why we think, feel, and behave as we do. But Scripture teaches that to fully comprehend the mind, we must first understand the heart, the source from which all thoughts, desires, and actions flow.

Scripture is clear:

“As a man thinks in his heart, so is he” (Proverbs 23:7).

“For the mouth speaks what the heart is full of” (Luke 6:45).

“For the word of God is alive and active. 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” (Hebrews 4:12).

“For from within, out of the heart of man, come evil thoughts, sexual immorality, theft, murder, adultery, coveting, wickedness, deceit, sensuality, envy, pride, foolishness” (Mark 7:21-22).

“Above all else, guard your heart, for everything you do flows from it” (Proverbs 4:23).

“For it is with your heart that you believe and are justified, and it is with your mouth that you profess your faith and are saved” (Romans 10:10).

A Case for the Heart

For centuries, philosophers, and theologians wrestled with the relationship between the heart, mind, will, and soul, seeking to understand not simply how we think, but what ultimately moves us to act. The study of human nature began with a study of the inner life and the heart that guides it.

Aristotle, even without Christian understanding, believed the heart was the governing center of human life. He asserted the heart was responsible not only for physical functions but also for the processes that directed human action. Going deeper, Saint Augustine of Hippo taught that we are shaped by what we love. When our loves are rightly ordered, with God above all else, our lives are rightly ordered.

Thomas Aquinas further characterized the affections of the heart as one’s innermost desires that shape behavior. Though he distinguished intellect from will, he described the “heart” as representing the will, which moves human action.

In his “Large Catechism,” Martin Luther stated, “That to which your heart clings and entrusts itself, is, I say, really your God.” Whatever captures the heart directs your life decisions.

In “Institutes of the Christian Religion,” John Calvin described the human heart as a “factory of idols.” When misplaced loves fuel our desires, they compete with our devotion to God.

In “Religious Affections,” revivalist Jonathan Edwards argued our deepest inclinations, the affections of the heart — not the mind — are what move us to action. That which we truly love determines how we live.

C.S. Lewis argued in “The Abolition of Man” that moral formation requires more than simply teaching people what to think. It requires training our affections to love what is good, reject what is evil, and honor what is worthy. He called these “ordinate affections.”

Lewis warned that when education develops the intellect without cultivating the affections, we produce what he famously called “men without chests,” people who may know what is right but lack the rightly ordered loves necessary to choose it. It is a trained heart that enables truth to become virtue expressed in life.

His point was profound: We must not only know the good; we must learn to love the good.

The Formation Gap

In our pursuit of understanding human nature, we lost sight of the psychology of the heart. Modern thought moved in another direction. Industry experts increasingly looked to the mind to understand and address what Scripture locates in the heart.

We focus on what people know and think while neglecting what they love and believe. We study what people do without asking what they desire. We manage behavior without considering what governs it.

Instead, let us recall the wisdom of Scripture. To remove the heart as the command center is to separate us from the source of our existence. Luke 6:45a tells us, “A good man brings good things out of the good stored up in his heart, and an evil man brings evil things out of the evil stored up in his heart.”

The next great advancement in our understanding of human nature will not come from discovering something new, but from recovering something we have forgotten. The mind does not operate independently of the heart. It is the content of the heart that determines what we will think, say, and do.