In Plain Sight, But Deliberately Ignored
Modern psychology, despite its remarkable empirical achievements, has suffered a profound philosophical amnesia: it has systematically marginalized or outright rejected the soul, the very concept from which its name is derived, as it was once defined as the “science of the soul” (psyche + logos).
While this article shares key points with our previous discussion on positivism and scientific reductionism, here we focus specifically on how this rejection is not merely a shift in terminology, but the consequences of limiting human reality to the measurable, the physical, and the observable. Why has psychology turned away from the soul? What has been lost in this process? And how might Thomistic philosophy provide a path back to a richer understanding of the human person.
The Soul Erased
How Modern Psychology Narrowed Its Focus
From the early 20th century onward, psychology redefined itself in strictly empirical terms, as Brennan, Gruender, Mercier, and Allers have documented. Hubert Gruender famously called modern psychology a “psychology without a soul," noting that the discipline, eager to avoid metaphysical entanglements by considering them non-scientific, deliberately shed the notion of a substantial, immaterial soul. Instead, it clung to what could be measured: behavior, neural activity, stimulus-response patterns, and reports of conscious states.
This rejection of the soul was not an isolated philosophical choice but a byproduct of two broader intellectual currents: the dualism of Descartes — which separated mind and body so sharply that later thinkers dissolved the mind into mere mechanism — and the positivism of figures like John Stuart Mill, who declared only the empirical as knowable. Here, the overlap with scientific reductionism becomes clear: psychology, seeking the prestige of the natural sciences, reduced human life to physiological or behavioral data, ignoring the spiritual substrate that the Thomistic tradition holds essential.
Why Is This Troubling?
Personal Identity
Without the soul as a substantial, unifying principle, psychology struggles to account for the unity and identity of the person over time. Gruender and Mercier point out that the enduring “I" — the experience of being the same person despite bodily and mental change — is inexplicable if we view the human as merely an aggregate of shifting physical or conscious states.
Intellectual and Volitional Acts
The higher faculties of the human being — intellect and will — cannot be reduced to biochemical processes without distortion. Thomists like Brennan and Mercier argue that intellectual acts, which grasp universals and necessary truths, transcend the material order by their very nature. Without admitting an immaterial principle like the soul, psychology either denies these faculties outright or reinterprets them in a reductionist framework, losing sight of their true nature.
A Practical Example of These Deviations
If the person is conceptualized solely as a tangle of physical and chemical processes operating without any organizing principle, then the experience of psychological distress that characterizes many mental disorders — egodystonia — makes no sense, because only a being that enjoys substantial unity can recognize that its different parts are not in harmony — in this case, its sensory and rational faculties, which, like branches of a tree, extending from the same trunk, or rather, the essence that makes this tree a tree.
Let's take a step further and return to the human level. If soul-less psychology theorists were correct, mental disorders such as depersonalization should not even exist, and yet people report experiencing themselves as “detached from their body.” In doing so, they recognized that there is a substantial principle that transcends matter, providing continuity and self-awareness — something that the study of biophysical processes cannot explain in a living being because matter it is not self-reflective, not at least in itself.
Recovering the Full Human Picture
Integration of Philosophy and Empirical Psychology
Crucially, this approach allows psychology to engage empirical data (neurological, behavioral, cognitive) without reductionism. Empirical methods are vital, but they must be joined to deeper reflection on what the data imply about human nature.
This is why Thomistic tradition not only distinguish between the science of psychology and the philosophy of psychology — which seeks to understand the underlying nature or substance of the human being —; but also recognizes these two approaches are complementary. As Brennan notes, the scientific side is “peripheral” (looking at surface operations), while the philosophical side is “central,” probing the core of being.
After all, no act of intellect occurs without its material underpinnings (brain activity, sense data), but neither can these underpinnings exhaustively explain the act itself. In this sense, while neuroimaging may reveal patterns of brain activation during decision-making, it cannot capture the intentionality, moral deliberation, or rationality involved — these belong to the spiritual dimension of the soul.
Restoration of final causality or purpose
Modern reductionism tends to regard any talk of purpose as unscientific — scientists, as Gilson said, would rather accept “blind force” than admit purposiveness. Thomism, however, always included final causes alongside efficient causes. Human actions are not just pushed by blind forces; they are also pulled by goals, ends, and meanings perceived as good.
Following on from the previous point, and as Cardinal Mercier insisted, we should “bring the wisdom of past ages to bear upon the latest triumphs of science,” harmonizing modern findings with perennial truths. Doing the opposite prevents contemporary psychology from understanding the results of its research on happiness and mental health, which consistently show the importance of meaning, hope, and a sense of calling for human flourishing — categories that make much more sense when one acknowledges a spiritual soul oriented to transcendent ends.
Recognition of Spiritual Faculties
By affirming that the human soul has rational and volitional powers irreducible to matter, Thomism not only strengthens the possibility of understanding phenomena related to psychopathology, but also defends the reality of free will, moral agency, and the human capacity for transcendence.
Rather than treating free will as an illusion, Thomism sees free choice as a power rooted in our spiritual rational soul. This has practical ramifications: therapies and interventions can appeal to a person’s capacity for choice — not merely attempt to recondition behavior.
In short, Thomism brings back the concept of the person as an integrated whole: intellect and will informed by a spiritual soul, operating through a physical body. Such a vision can inspire research that respects both our measurable and immeasurable spiritual nature.
Toward a Psychology with Soul
The rejection of the soul and spiritual dimension in modern psychology is more than a semantic or academic issue; it is a rupture that has profound consequences for how we understand, heal, and guide human beings. The Thomistic tradition offers a robust framework to weld this rupture, reminding us that to study the human being is ultimately to study a composite of matter and spirit, body and soul.
The invitation is open for today’s psychologists and scholars: to enrich their empirical research with metaphysical insight, and in doing so, to reunite the fragmented pieces of the person into an integral whole. Only then will psychology truly know the psyche it seeks to understand — not as a hollow ghost or a cerebral accident, but as the living soul of a living person, imbued with meaning and oriented toward truth.
Nicolás Eyzaguirre Bäuerle
Editor-in-chief
