MBTI Function Theory For Beginners: It's Not About Your Personality

The benefits and limitations of typing are this: it may assist you to understand what kinds of information you and different people may have perceived, and what you and they may use that information to accomplish. This can be useful. For example, wording things nicely matters more to someone who uses Fe, while being straightforward is best with someone who uses Te; an Ne user may talk for a long time if you get them on a certain subject, but an Se user will get distracted quickly; an Fi user will behave morally for moral's sake while a Ti user will behave morally because it doesn't make sense not to; if presenting a project to one's boss, an Si using boss will want data on what has worked in the past, while an Ni user will just want proof that your project will work in the future. You can't always predict how people will react, but you can be a little more prepared.

Because of the way it works, I prefer to consider MBTI a psychological theory, rather than a personality theory. A lot of things go into your personality, including what you ate for breakfast, but MBTI is about a heierarchy of awarenesses and ways to make decisions which is a bit more specific than personality.

First of all, MBTI isn't just four letters. It's eight functions. The functions each signify a different kind of awareness or decision making process. There are six different kinds of functions, which you may know as the first three letters on any given type. They are as follows:

E (extroversion) - external awareness (takes information/tools from current surroundings)
I (introversion) - internal awareness (consistently builds upon stored information/tools from the past)
S (sensing) - physical/factual awareness (real/concrete information)
N (intuition) - abstract/theoretical awareness (possible/theoretical information)
F (feeling) - emotional awareness and decision making
T (thinking) - logical awareness and decision making


I have written my most succinct descriptions yet of the functions themselves. I also explain what they might look like, though that is more for convenience and clarity and does not apply to everyone who uses the function.

Se: An external physical/factual awareness. Se notices and identifies the bare reality of it's surroundings separate from any abstract interpretation or possibilities. It is only what is. 

May be characterized by a realistic perspective of one's situation, impulsive actions caused by not thinking ahead, or a high level of physical aptitude.

Si: An internal physical/factual awareness. Si notices and identifies the bare reality of it's own being, separate from any abstract interpretation or possibilities. It is what it is according to the internalized facts which it is continually building upon. 

May be characterized by an adherence to longstanding personal tradition, practicality based on known facts, or an awareness of how one's body is working.

Ne: An external abstract/theoretical awareness. Ne notices and identifies the possibilities presented by it's surroundings which may not yet be reality or presented as facts. 

May be characterized by unique theories and concepts, requiring of external mental stimulation, thinking out loud, a deep understanding of complex theories such as language, and distractedness.

Ni: An internal abstract/theoretical awareness. Ni notices and identifies theoretical concepts based upon information already internalized and builds upon it's theories continually as more facts are presented to it to work with. 

May be characterized by in-depth understandings of complex theories and concepts, an ability to see probabilities far in advance (strategic capability), and by processing unconcluded concepts quietly in one's head rather than out loud.

Fe: An external emotional awareness and decision making process. Fe recognizes and utilizes the emotional situation/atmosphere in those around it. 

May be characterized by an easy ability to empathize with others and provide their needs accurately, relief when expressing emotions, emotional manipulation, or an interest in keeping up appearances.

Fi: An internal emotional awareness and decision making process. Fi recognizes and utilizes it's own emotional situation/aura. 

May be characterized by a desire to match outward action to inner convictions, difficulty in changing one's mind about emotional opinions, or application of one's own emotional response to relate to another.

Te: An external logical awareness and decision making process. Te recognizes and utilizes the systems and patterns surrounding it. 

May be characterized by direct language, a quickly perceived understanding of how systems and patterns function to create results, goal-orientation, managerial sense, business sense, financial sense, uninhibited free-flow of opinions, or harsh words.

Ti: An internal logical awareness and decision making process. Ti recognizes and utilizes it's own collection of systems and patterns. 

May be characterized by complex problem-solving, puzzle aptitude, solves problems on own without asking for help, unbiased observation, or difficulty in accepting advice that does not compliment one's idea of logic.


MBTI recognizes sixteen different personality types, each of which arranges those functions in a specific order. This order always puts two functions at the top of the stack that are most important. If we ignore which of those two is dominant, we only have eight types, which makes it easier to explain.

SFJ - Si and Fe - prefers to orient thinking around a lifelong gathering of perceived physical/factual information and make decisions based upon the emotional atmospheres provided by others

SFP - Se and Fi - prefers to orient thinking around currently presented physical/factual information and make decisions based upon the emotional aura/situation one experiences/has experienced

NFJ - Ni and Fe - prefers to orient thinking around it's lifelong gathering of internalized theoretical concepts and make decisions based upon the emotional atmospheres provided by others

NFP - Ne and Fi - prefers to orient thinking around currently presented theoretical concepts and make decisions based upon the emotional aura/situation one experiences/has experienced

STJ - Si and Te - prefers to orient thinking around a lifelong gathering of perceived physical/factual information and make decisions based upon the external systems and patterns currently presented

STP - Se and Ti - prefers to orient thinking around currently presented physical/factual information and make decisions based upon the web of systems and patterns in which it is constantly building

NTJ -  Ni and Te - prefers to orient thinking around it's lifelong gathering of internalized theoretical concepts and make decisions based upon the external systems and patterns currently presented

NTP - Ne and Ti - prefers to orient thinking around currently presented theoretical concepts and make decisions based upon the web of systems and patterns in which it is constantly building

Obviously there's a lot more information about how all of the functions work together and so on, but I just wanted to shoot out a basic template of what this theory is about at it's core.