Unfolding Essence: On the Human Growth
We’ve all watched a baby stretch into childhood, a clumsy teenager getting used to the new size of his limbs, and a young adult reach his full stature. And yet, as familiar as these changes may be, it’s not always clear why a snowball that increases in size as it rolls downhill is not “growing" in the human sense. What is the difference?
This question lead us beyond biology into philosophy. In the Aristotelian-Thomistic tradition, human growth is not simply an external event or an accidental aggregation of cells. It is an immanent action of the soul—the substantial form of the body—moving the human being from potency to act, from what can be, to maturity. Understanding this process reveals human development not as a purely material occurrence, but as a meaningful unfolding of life toward its final end.
What Is Growth?
The Vegetative Soul in Action
In Aristotelian-Thomistic psychology, all living beings are composed of matter and form—the form in living beings is called the soul. Every act of life is made possible by this animating principle. And at the base of all vital activity lies the vegetative soul, which governs three operations: nutrition, growth, and generation. These are not metaphorical or vague attributions, but distinct, identifiable faculties. As St. Thomas Aquinas writes, growth is a proper operation of the vegetative soul—not a byproduct of other processes, but its own power—vis augmentativa—directed toward a specific end: the full development of the living organism.
Importantly, growth is not the same as nutrition. Nutrition preserves and restores what already is. Growth, however, increases the body’s quantity so it can reach its natural completion. In Thomistic terms, nutrition preserves being, but growth perfects it. To illustrate, consider the difference between feeding a fire and feeding a child. A fire “consumes” fuel and produces heat—its process is essentially destructive. But a child assimilates food, transforms it into living tissue, and builds upon it.
The Teleology of Human Growth
This inner-directed transformation is what Thomists call immanent action—acts that remain within and perfect the agent. Unlike stacking bricks for building a wall—which is a transitive action terminating in something external—growth transforms the agent itself. The food that nourishes a child becomes her bone, her flesh. As Aristotle observed and Thomists affirm, inanimate things, such as a snowball rolling down a hill, may become bigger by juxtaposition, but only living things grow through assimilation. This marks a radical ontological difference between living organisms and machines. A car is assembled from parts; a person unfolds.
Such unfolding is not haphazard, but teleological. That is, it has an end, a telos. St. Thomas affirms that “growth is ordered to the due quantity of the living being”—it aims toward a fullness proper to the organism’s nature. In a child, that fullness includes not only stature and strength, but cognitive ability, emotional intelligence, and moral capacity. In other words, growth moves toward maturity, not by chance, but by nature’s inner directive. This orientation reflects the metaphysical structure of life: the soul organizes matter toward specific ends.
This is why Thomists speak of the form as both efficient and final cause. It initiates activity and directs it to its end. In growth, this means that the soul is not only what causes the body to grow, but also what determines how much and in what way. The soul knows, in a sense, what the adult human should become—even before the intellect awakens to it.
Growth and the Unity of the Soul
In a human being, the soul is not three but one: the rational soul. However, it virtually contains the powers of the vegetative and sensitive souls. This means that while we act as rational beings, our rational soul also encompasses the life-powers we share with animals (sensation, appetite, movement) and with plants (nutrition, growth, generation). We are not a bundle of separate souls working in tandem, but one unified principle of life unfolding through ordered levels.
Thomism presents these powers hierarchically: each higher faculty presupposes and perfects the lower. Thus, growth is not merely a background process—it's the ground upon which more advanced operations like cognition, volition, and moral choice are made possible. A starving body cannot think clearly, and a stunted brain cannot learn. As the roots nourish the tree’s fruit, so growth supports all rational activity. But more importantly, the higher orders the lower toward a higher good. A child’s physical growth enables her to walk, then run, then dance; her little mouth goes from babbling to saying her first words, and then not just those of her mother tongue. In each case, the vegetative lays the foundation, but the sensitive and rational powers complete and dignify the movement.
Indeed, the path from infancy to maturity maps this metaphysical hierarchy: first comes nourishment and growth; then sensation, desire, and motor coordination; and finally self-awareness, reasoning, and moral agency. Human development, then, is not simply biological maturation but the unfolding of the soul’s entire power in time.
Practical Implications
Development as a Measure of Vital Health
Viewing growth as an immanent act of the soul has powerful consequences, especially in medicine and developmental psychology. Physical growth is not just a biological metric; it is a visible sign of the soul's formative presence. When growth is delayed or disordered, it may indicate more than a nutritional deficiency—it may reflect a deeper disharmony in the soul-body unity. Modern studies on psychosomatic illness and childhood trauma confirm what the tradition has long taught: growth requires not only food, but love, stability, and the integrated function of the whole person.
This vision also elevates the importance of pediatric care, early education, and family life. To foster human development is to assist the soul’s own operations. A parent who provides nourishing meals and consistent affection is not merely “supporting biology,” but cooperating with the soul’s self-perfective activity.
Human Growth and Education
From this view, education itself is a continuation of growth. The intellect and will—higher faculties of the soul—develop upon the foundation laid by vegetative and sensitive functions. Thomists affirm that “nothing is in the intellect that was not first in the senses.” But those senses, in turn, depend on the proper growth of the body: clear vision, stable nervous systems, and so on.
A child who has been rightly nourished and matured physically is more apt to grow in judgment, creativity, and virtue. In this way, the intellectual growth of the person presupposes—and crowns—the physiological growth of the body. Education, then, is not a separate process from growth but its flowering.
Ethical and Spiritual Dimensions
On a moral and spiritual level, growth takes on even greater depth. Since growth is teleological—ordered to perfection—then stunted growth is not merely a tragedy but a failure of purpose. It may result from deprivation, trauma, or the refusal of interior effort. This is why the Catholic tradition speaks of growing in virtue or maturing in grace. These metaphors are not rhetorical flourishes. They express the soul’s deepest longing: becoming what it was meant to be.
Indeed, the Christian view of salvation itself is cast in terms of growth. Grace does not override nature but perfects it. Sanctification is the flowering of the soul’s capacity, elevated and fulfilled by divine life. Here, growth is not outgrown; it is glorified.
Toward Our Full Stature
Growth is not merely an increase in size; it is the unfolding of a form, the realization of what we already are in potential. Thomism insists that we are not a collection of faculties loosely tied to a body. We are unified beings whose every motion—from cell division to contemplation—proceeds from a single principle of life: the soul.
In this light, growth is not just a phase of childhood or a physical process to be tracked. It is the invisible artisan shaping a rational being. To grow is not to become someone else, but to become fully ourselves. And though our bodies will one day cease to grow, the soul’s final increase remains ahead: not in inches or achievements, but in the measure of love. For we were made not only to grow, but to be made perfect in Him who gave us life.
Nicolás Eyzaguirre Bäuerle
Editor-in-chief
