Psychology’s Blind Spot

Imagine a scientist who proudly refuses to use a microscope, insisting that only what can be seen with the naked eye counts as scientific data. Microscopic structures of tissue, the cells that compose it or microbes that have infected the sample — would be dismissed as irrelevant because they escape unaided vision. Such a scientist would not merely miss details; he would blind themselves to entire realms of reality.

This striking analogy captures the predicament faced when introspection is excluded from psychological science. By discarding the “inner gaze," psychology risks reducing the person to observable behaviors and brain circuits, forsaking the rich interiority that makes us human. How did this exclusion arise, and can anything be done to recover it? Drawing on the Aristotelian-Thomistic tradition, we will argue that the exclusion of introspection represents not just a methodological choice but a deep error that has fragmented the field, reducing the human person to parts.

What Is Introspection?

Introspection, from the Latin introspicere (to look within), refers to the first-person observation of one's own mental states: perceptions, thoughts, feelings, and so on. Unlike external measurements, introspection makes the subject into an object of study. Early psychologists like Wilhelm Wundt and E. B. Titchener believed that rigorous self-observation, combined with experimental conditions, could reveal the elements of consciousness. Philosophers, long before the advent of laboratory psychology, had relied on reflective awareness to explore the nature of mind and soul. Aristotle and Thomas Aquinas, through philosophical introspection, derived profound insights about the immaterial intellect, free will, and the unity of the person — insights accessible to all humans through common experience.

As Brennan notes, the facts of such philosophic introspection are public property — available to any attentive person — and, in this sense, they carry objective validity for all humans. In other words, if an introspective report truly reflects a universal aspect of human nature — for instance, “we all seek happiness” or “I can reflect on my own thoughts” — , then it is not a private whim but a window into human reality.

The Fall of Introspection in Psychology

Yet by the early 20th century, introspection came under attack. Behaviorism, led by John B. Watson, declared introspection “unscientific" because it lacked external verifiability. In his 1913 manifesto, Watson proposed a psychology that studied only observable behavior, dismissing consciousness and subjective experience as epiphenomenal or irrelevant. As Brennan observed, psychology, having already lost the soul, now proceeded to abolish consciousness itself from its domain.

This exclusion reflected deeper philosophical currents. Auguste Comte and other positivists rejected introspection on principle, arguing that one cannot be both observer and observed simultaneously. Materialist philosophies reinforced this stance by treating inner experience as either illusory or reducible to neural mechanisms. Psychology thus became the science of stimulus and response, inputs and outputs, treating the mind as a black box whose inner workings were either irrelevant or unknowable, leaving the inner life behind.

Not everyone was happy with this one-sided direction. Some psychologists — most notably the Gestalt psychologists in Europe, and later the humanistic psychologists — kept interest in subjective experience alive, while in the fields of psychiatry and psychotherapy, introspection was impossible to ignore. For example, Sigmund Freud relied on patients’ verbal reports of thoughts and dreams to psychoanalyze the unconscious mind. Still, for decades, the dominant academic psychology remained aggressively anti-subjective, and therefore, preached against introspection.

Why Is This Troubling?

Losing Access to Interior Life

The rejection of introspection had far-reaching consequences. First, it deprived psychology of direct access to the qualitative, lived experience of the human being. As the Thomistic tradition emphasizes, certain phenomena — such as the subjective feel of pain, the intentionality of thought, or the interior experience of deliberation — are not externally observable but are nonetheless real and integral to human psychology. Without introspection, such phenomena disappear from scientific view.

Brennan notes that without interior observation, psychology risks mistaking its object: it ends up measuring peripheral effects while missing the essential core. For instance, by focusing solely on behavioral outputs, psychologists may fail to grasp the inner dynamics of moral decision-making, reducing freedom to an illusion of conditioned responses.

Tearing Apart The Experience of Oneness

To return to our opening analogy: a scientist who refuses the microscope misses microbes, while analogously, a psychologist who refuses introspection misses consciousness and intentionality, as mentioned above. However, what is probably more concerning is that he loses sight of the experience of oneness.

Aquinas observed that every sensation or emotion has “a synthetic quality and a character of oneness", meaning that even though multiple cognitive and affective processes are involved, we experience them as a unified whole. This is not just a collection of disconnected reactions; it’s a single, integrated experience. Without introspection, this unifyed awareness vanishes from view. Furthermore, due to a third-person analysis — which is incapable to access to the experience of oneness — the psyche is fragmented and studied as isolated functions, disappearing the person as an integral subject.

Splintering into Incomplete Theories

Because of the later, the exclusion of introspection also fragmented psychology into competing schools, each emphasizing a partial truth. Behaviorists explained behavior in mechanical terms; Freudians reduced inner life to unconscious drives; cognitive scientists modeled the mind as an information processor. But without an integrating vision grounded in the lived unity of consciousness, these models remained disconnected and incomplete.

Brennan lamented that psychology students could recite the differences between these schools but could not answer the fundamental question: What is psychology about? Without introspection to unify the interior and exterior, psychology lost coherence as a science of the whole person.

Restoring Introspection in an Integrated Framework

From a Thomistic standpoint, introspection remains indispensable because it provides direct access to the operations of the intellect and will, which cannot be fully captured by external observation. As Aquinas practiced, introspection is not mere subjective rumination but a systematic reflection on the acts of the soul. By attending to our own acts of knowing, willing, imagining, and feeling, we abstract universal principles about human nature.

The Thomistic tradition proposes a methodological integration: introspection provides hypotheses and insights about internal processes, which can then be tested, clarified, or complemented by empirical observation. Rather than pitting subjective and objective methods against each other, this approach views them as mutually enriching.

Underlying this integration is the Aristotelian-Thomistic metaphysics of hylomorphism: the human being is a composite of body (matter) and soul (form). This unity implies that conscious experience is manifested through bodily operations, but cannot be reduced to them. Therefore, both internal and external perspectives are necessary to grasp the full reality of the person.

By restoring introspection, psychology regains access to the interior life that constitutes the essence of its subject. This inclusion allows psychology to explore questions of intentionality, freedom, meaning, and moral agency — dimensions that behaviorism and materialist models tend to obscure or ignore.

Willing To Use The Microscope

The exclusion of introspection from modern psychology represents more than a omission; it signals a impoverishment, a loss of vision for what it means to be human. By turning outward to measurable phenomena alone, psychology became a science without an inner gaze, forgetting that to know the human is to know the living, conscious, willing subject.

Aristotelian-Thomistic philosophy invites psychology to open that inner gaze once again — to look within, not in rejection of empirical rigor, but in fulfillment of it. Only by integrating introspection with external observation, and grounding both in a metaphysics of the soul-body unity, can psychology hope to achieve a comprehensive understanding of the human person. In the end, this is the promise of a truly integrated psychology: a science faithful to the whole of reality, including the deepest interior life of the human person.

Nicolás Eyzaguirre Bäuerle

Editor-in-chief