The Open Question of the Third Function — e or i?
In recent years, I have independently deepened my study of Carl Jung’s theory of types and the models that developed from it, including MBTI. Along the way, I discovered that this is a tool that can greatly contribute to self-understanding, improving relationships, and personal development — but also a tool that raises quite a few questions and criticisms, especially regarding the way Jung’s original theory was translated and made accessible by The Myers-Briggs Company.
One of the questions that raised doubts for me concerns the status of the third cognitive function in the type structure. In some official MBTI materials, there is a claim that the third function does not necessarily have a fixed orientation, meaning it can be introverted or extroverted regardless of the type’s first function. For example, instead of presenting INTJ as having a defined function sequence of Ni, Te, Fi, Se, there is sometimes an option in which the third function is marked only as F, without determining whether it is Fi or Fe.
In my view, this approach is not only vague, but also misses an essential part of the Jungian structure of personality. When the third function is left “open,” it effectively undermines the internal logic of the entire model — a model based on dynamic relationships between opposites and symmetry between the different forces in the psyche. In this article, I will try to explain why I believe this view is problematic, why it is not sufficiently supported by research or professional literature, and how a more precise understanding of the third function can significantly deepen our understanding of type and the process of personal development.
So what did Myers-Briggs, the company, actually say?
So the exact wording used by the Myers-Briggs organization regarding the orientation of the third function is: “There is disagreement about the orientation of the third function, with some experts saying that if the first function is extroverted, for example, then all the energy goes to it, and the remaining three functions will be introverted because they receive less energy. Others argue that in order for there to be true balance, the third function must be completely opposite to the first, both in its kind and in its orientation.” The Myers-Briggs organization left room for each person to choose, based on their own experience, which direction the third function faces.
In doing so, they did not really determine anything, but simply said: there is no agreement on the subject, some think this way and some think otherwise, you decide for yourselves, we are not getting into it...
Who are these “experts,” actually?
The experts that “Myers-Briggs Ltd.” are referring to are bloggers and other people in the world of types. There is quite a bit of discussion around “what Carl Jung meant when he said that the final functions must be opposite to the primary one” — but there is no empirical research or official source that makes this claim. Most independent researchers in the field of types agree with the more conventional model of the functions: INTJ — Ni, Te, Fi, Se.
The very fact that “Myers-Briggs” themselves do not seem fully convinced about the third function being opposite in orientation to the first should be a strong enough argument that this statement is not correct. But to remove any doubt, here is a detailed explanation and several additional reasons. Later, I will also explain why the conventional model is more logical and harmonious.
Reasons why the statement that the third function “can be either introverted or extroverted” is not correct:
1. Myers-Briggs have not published any findings, statistics, or studies supporting this claim. They claimed that there are mysterious “experts,” but did not quote them or mention them by name. Their statement is very generic and provides no reference to research literature, sources, names of researchers, or any findings.
2. The “experts” they are referring to are most likely bloggers and people from the world of typology who discuss among themselves interpretations of Jung. “Most likely,” because they have never bothered to publish even a single name of a researcher behind the claim. These bloggers do not have a consensus, and most of these discussions are only hypotheses, without any research support.
3. The Myers-Briggs Company operates as a commercial body in every sense, whose central goal is selling assessments and generating revenue, not necessarily advancing open scientific research in the field of personality. Accordingly, a significant portion of the data, measurement methods, and empirical foundations are not fully accessible to the research community, which prevents orderly critical examination or a process of peer review.
In practice, the lack of research transparency also allows for a very flexible interpretation of questionnaire results: when a person does not “fit smoothly” into one of the categories, this can be explained as a functional deviation or as the reversal of a certain function, instead of acknowledging the possibility of overlap between types or the limitations of the tool itself. In this way, the model maintains a higher reported level of “accuracy,” but sometimes at the expense of genuinely clarifying the complexity of personality.
Therefore, when there is extensive research literature offering alternative or more critical models, it is difficult to justify automatically accepting Myers-Briggs findings as the exclusive basis for understanding personality.
4. The MBTI questionnaire was built on an existing theory — from which many additional theories and studies emerged, including Socionics, John Beebe, Linda Berens, Keirsey’s four temperaments model, Dario Nardi, Jungian psychologists who interpreted his writings, and many others — which are not subject to the Myers-Briggs Company or its procedures. It is not right to ignore an entire ocean of additional research and findings in the field, which, unlike Myers-Briggs, did make efforts to conduct empirical studies, report their findings, and collect data. Quite a few independent researchers support the conventional model.
Research and findings in the field
1. When examining the broader literature that developed around Carl Jung’s ideas, we see that most of the deeper models of type do not treat the third function as “undefined” in its orientation, but as part of a symmetrical structure. In other words, if the first function is introverted, the third function is also introverted; if the first is extroverted, the third is also extroverted. The reason for this is that the functions are not a random list of preferences, but a balanced system of opposites.
2. John Beebe’s model also strengthens the classical understanding of the third function, but not because he “simply decided so.” Rather, his entire theoretical structure rests on this. Beebe expanded Jung’s four-function model into a model of eight archetypal functions, in which every conscious function has an unconscious shadow in the same form but with the opposite orientation. This structure is possible only if the four primary functions themselves are arranged in consistent symmetry — meaning the first and third share the same orientation, and the second and fourth share the opposite orientation.
If the third function could be introverted or extroverted arbitrarily, the entire archetypal parallel that Beebe proposes would break down: there would be no clear correspondence between the ego and the shadow, and the model would lose the symmetry on which it rests. In other words, the very fact that Beebe’s model works as a complete system and corresponds with clinical experiences of patients strengthens the assumption that the third function does not change its orientation randomly, but is preserved according to the structure of the type.
3. Dr. Dario Nardi’s work also strengthens the classical model. In his studies, which examined brain activity using EEG among people of different types, consistent patterns were found in the activation of certain brain regions according to the cognitive preferences of the type. Among INTJs, for example, activity patterns were found that correspond more closely to the classical Ni–Te–Fi–Se sequence. In particular, activation was observed in areas related to internal personal processing, subjective evaluation, and the formation of an independent value-based stance — characteristics associated with Fi. In contrast, according to the findings he published, this profile did not show significant activation of the areas he associates with Fe, meaning processes of emotional synchronization with the environment, reading the social situation, and adapting to group harmony.
The meaning of these findings is that this is not only a theoretical interpretation of Jungian writings, but also a physiological indication: when the brain activity patterns of people identified as INTJ were examined, support was found for patterns corresponding to Fi as the third function, and not to Fe. Therefore, the claim that the third function can be “either introverted or extroverted” without importance to the type structure is not supported by the empirical findings of one of the central researchers in the field either.
4. If Fi is replaced with Fe in INTJ types, the result is a structure in which both Te and Fe operate as extroverted judging systems. In such a structure, all the evaluative mechanisms of the personality are directed outward — one through objective and practical logic, and the other through emotional-social dynamics. The result is that there is no stable internal value anchor organizing these two systems from within.
But here a deeper structural problem emerges: two extroverted judging functions cannot operate as parallel axes of decision-making without entering into constant tension. Te and Fe define what is “correct” and “appropriate” according to different, and even conflicting, criteria — one sets functional-systemic truth, while the other sets interpersonal harmony. When both are placed in an external controlling position, there is no internal hierarchy that decides between them, and therefore every decision becomes fluctuating or dependent on the situation rather than on structural consistency.
In such a state, the personality loses the ability to be principle-oriented. Instead of integration between logical and value-based judgment, what emerges is a system of “two external judges” competing with one another, without a mediating factor that defines what should take priority when they clash. This is exactly what undermines the fit with the INTJ model, which is based on the idea of an organizing internal core, Fi, that filters both the efficiency of Te and the value meaning of the social world.
5. In fact, the moment we give up on the orientation of the third function, we lose a significant part of the ability to understand the type beyond stereotypes. A person may appear very logical or very sociable outwardly, but the difference between Fi and Fe as the third function completely changes the internal structure: Are their values built from personal truth, or from a social-emotional field? This is not a small question — it is the heart of personality.
The philosophies that influenced Jung
Carl Jung did not develop his ideas in a vacuum. He was deeply influenced by ancient traditions: alchemy, Gnosticism, Christian mysticism, Taoism, and the philosophy of complementary opposites. For him, the psyche was not a collection of traits, but a dynamic system of balances, in which every force creates and complements its opposite.
This idea is especially prominent in the alchemical concept of the union of opposites. The alchemists saw nature as a system in which every element carries its opposite: sun and moon, masculine and feminine, matter and spirit. Jung adopted this idea directly into psychology: every conscious position gives rise to a complementary unconscious position.
If we apply this to the functions, the classical order creates a harmonious structure:
The dominant and fourth functions are complete opposites, for example Ni versus Se.
The auxiliary and third functions are also opposites, but at a different level of consciousness: Te versus Fi.
This creates a symmetrical system in which every force has a counterpart and a complement.
When it is said that the third function “can be either introverted or extroverted,” this symmetry is broken. The model no longer behaves like an organic system of opposites, but like a random collection of functions. This may be convenient for simplifying a questionnaire, but it distances us from Jung’s original ideas about the structure of the psyche.
In other words: if we give up the consistency of the third function, we do not only lose accuracy in typing — we also lose the internal logic of the entire model.
Conclusion — Stop Guessing, Start Understanding
The debate over the orientation of the third function may at first seem like a technical or theoretical disagreement only, but in fact it has deep implications for the way we understand personality, development, and growth. If we treat the third function as something “open to interpretation” without a clear structure, we lose a central part of the logic of the Jungian model: the idea that the psyche operates through systems of complementary opposites, and that every part of the personality exists in mutual relation to the others.
For me, this is also the difference between using MBTI as a commercial questionnaire that provides labels and using it as a tool for inner observation. When we understand that the third function maintains the same orientation as the first, the possibility opens up to see deeper layers of personality — not only what the person presents outwardly, but also their inner world, their conflicts, and the direction in which their individuation process may develop.
Therefore, in my view, insisting on the classical structure is not “conservatism” or blind adherence to tradition, but an attempt to preserve the depth of the model. Carl Jung’s model was meant to describe a living, complex, and symmetrical psychic system — not a random list of traits. The further we move away from this structure in favor of convenient simplifications or vague statements, the more we lose what made the theory so meaningful in the first place: its ability to explain not only how people appear on the outside, but how their psyche is organized from within.
Feel like you have more to say about this? Let’s continue the healthy debate in the group. We opened a WhatsApp group for people who understand — and are interested in — MBTI, where you can debate types without holding back: