The philosophical roots of Psychology
Human psychology, the field of interest of great thinkers
Since ancient times, people have been concerned with the mind, soul, or spirit. The word in Ancient Greek that defines these concerns is ψυχή (psyche). The word “psychology” is therefore composed of two words: “psyche” (soul) and “logos” (science) and literally means “the science” or “study” of the soul.
Among the most important philosophers of Ancient Greece are Plato, Aristotle[1] and Hippocrates (the father of medicine). As is shown throughout the article, they laid the foundations of the field that would come to be called “psychology”, their ideas being essential in formulating several theories about the human psyche.
The substrata of the mind: Plato vs Jung
A good example of an ancient Greek philosopher who conceptualized these questions about life is Plato. He developed the idea that the “psyche” is immortal and has three component parts: the rational, the spirited (courageous), and the appetitive (desires). [7]
Although it depends on which school one follows and which theory one finds convincing, the notion of “layers of the human mind” became established in mainstream psychology thanks to major thinkers and pioneers in the field, including Carl Jung and Sigmund Freud. Thus, more than two millennia before the publication of The Interpretation of Dreams (1900) and The Ego and the Id (1923) by Sigmund Freud, and The Archetypes and the Collective Unconscious (1959) by Carl Jung, someone had already thought about and conceptualized the substrata of the human mind.
Freud believed that the human psyche is composed of three such layers. In 1900, when he published Die Traumdeutung (The Interpretation of Dreams), he defined and named several of them (conscious, preconscious, and unconscious) [2], and in 1923 (Das Ich und das Es) he refined his theory. The human psyche, he said, is composed of the Id (instinctual and unconscious), the Ego (rational and partially conscious), and the Superego (where moral norms are located, partially unconscious). [3]
Carl G. Jung conceptualized these substrata in 1959, when he divided the human psyche into three major categories:
The conscious – the rational, active, and present part of the psyche, where the ego operates (self‑image, thoughts, and decisions).
The personal unconscious – specific to each person and including repressed memories, traumas, forgotten desires, psychological complexes, etc. It is formed from one’s own experiences but is not directly accessible.
The collective unconscious – a universal inherited psychic layer, common to all human beings. It contains archetypes: fundamental symbolic forms that structure human experience (e.g., the Mother, the Hero, the Shadow, Anima, Animus, the Self, etc.). It does not arise from personal life, but from an ancestral, mythological, and biological background. [5]
The similarity between these theories (Plato’s and Jung’s) is evident. Moreover, in the same book published at the end of the 1950s (though largely composed of manuscripts written between 1930–1950), Jung wrote:
“Plato was convinced that in man there exists a world of autonomous ideas, born not from the senses but from the soul itself. This conception is extremely close to the idea of the archetype*. [...] Platonic ideas are, in fact, archetypes of the soul.” [5]
The study of personalities. The modern era vs Antiquity
Hippocrates, the father of medicine, also made a contribution to psychology, perhaps surprisingly for some, by developing the “humoral theory”. [4]
He believed that human health and behavior are influenced by the balance of four bodily fluids:
Blood → sanguine temperament (energetic, sociable, optimistic)
Phlegm → phlegmatic temperament (calm, quiet, passive)
Yellow bile → choleric temperament (impulsive, aggressive, active)
Black bile → melancholic temperament (introspective, sad, creative)
Hippocrates wrote in the work “Peri Physeōs” (On Nature), attributed to the Hippocratic school:
“The human body contains blood, phlegm, yellow bile, and black bile. Health is maintained by the balance of these humors. Disease appears when one of them dominates or is eliminated in excess or in insufficient quantity.” — Corpus Hippocraticum, De Natura Hominis, ch. 4.
Over almost 2,500 years, Ivan Pavlov (especially known for discovering the conditioned reflex**) has linked the types of temperament to the physiological characteristics of the nervous system (starting from his observations about the canine nervous system).
Thus, in his work "Upper types of nervous activity", he correlated the classical temperament types theorized by Hippocrates with the characteristics of the nervous system: strength, balance, mobility of processes of excitation and inhibition. [6]
In a few decades, it will be Jung and Eysenck's turn to make an appearance, to refine these categories or introduce new ones. But I will stop here, not wanting to bore you excessively. What is important to note, however, is something else: Hippocrates' conceptualizations played an important role in temperament psychology and were the precursors of the theories formulated by Pavlov, Jung, and Eysenck.
Conclusion
The roots of modern psychology lie deep in ancient philosophy, where thinkers such as Plato, Aristotle[1] or Hippocrates laid the foundations for reflection on the human soul, reason, and behavior. Although language and scientific methods have refined over time, the great questions about human nature, identity and knowledge remain essentially the same. Studying the influence of ancient philosophy on psychology helps us not only to understand the origins of this science, but also to appreciate the continuity of ideas that shape, even today, the way we think about mind and behavior.
* In psychology, an archetype is a deep psychological pattern, with which we are born, which helps us to interpret the world and react to it, through universal images and symbols (Mother, Hero, Shadow, etc.).
** Pavlov noticed that after associating a sound (bell) with food, the dog began to salivate only when hearing the sound, even without food. This type of reaction learned – salivating to a neutral stimulus became signal – was called conditioned reflex and was the basis of classical conditioning theory, important foundation in behaviorist psychology.
Works cited
Aristotole. (1984). About soul. In the Works (Vol. 3). Bucharest: Scientific and Encyclopedic Publishing House. [1]
Freud, S. (1900). Die Traumdeutung [Dream interpretation]. Leipzig: Franz Deuticke. [2]
Freud, S. (1923). Das Ich und das Es [Eul and the Self]. Vienna: Internationaler Psychoanalytischer Verlag. [3]
Hippocrates. (trade. 1923). By Natura Hominis [About the Nature of Man], in Hippocratic Writings. Oxford: Oxford University Press. [4]
Jung, C. G. (1959). The Archetypes and the Collective Unconscious. Princeton, NJ: Princeton University Press. [5]
Pavlov, I. P. (1927). Conditioned Reflexes: An Investigation of the Physiological Activity of the Cerebral Cortex. London: Oxford University Press. [6]
Plato. (1996). Republic (trad. Andrei Cornea). Bucharest: Humanitas Publishing House. [7]
Additional reading
Kramar, E. (2012). Introduction to psychology. Iasi: Polirom. [8]
Zlate M (2000). Psychology's fundamentals. Bucharest: University Publishing House. [9]