The following article gets a bit complex but also provides important information if you want to understand personality type in any depth. If you don't understand what the eight cognitive functions are, please read about that first before you read the following. Otherwise, the following will be painfully unfamiliar jargon that will just frustrate and disappoint you, and might make you somewhat angry at yourself and/or the author. 

Here's a process to follow if you want to start getting the hang of how functions work. The overall principle here is that functions are a system of opposites that balance each other out. So, as you figure out the functions for each personality type you'll notice how this opposing and balancing dynamic works out.

Here's an example, an INFJ MBTI type means the person is:

  1. Introverted
  2. Intuitive
  3. Feeling
  4. Judging (we use the word "deciding" here because we consider the term "judging" to be antiquated and somewhat misleading.

When we’re converting from an MBTI type description to a functional type description, you figure out the first two functions first. This takes 3 steps:

  1. Find the first two favored functions. Items 2 & 3 above will always describe the first two favored functions, but we don’t know their attitudes yet (extraverted or introverted) and we don’t know their order. For example, intuitive (N) and feeling (F) describe the first two favored functions for an INFJ.
  2. Determine the attitude of the favored functions. A type that ends with J will always extravert their favored deciding function (Te or Fe) and introvert their favored perceiving function (Ni or Si). Likewise, a type that ends with P will always introverted their favored judging function (Ti or Fi) and extravert their favored perceiving (Ne or Se) function. INFJ ends with J so Feeling (F) is extraverted (Fe) and Intuition (N) is introverted (Ni).
  3. Determine the order of the favored functions. Since an INFJ is an introvert (the I in INFJ), the first function must be introverted. This means the first function must be Introverted Intuition (Ni) so the second has to be Extraverted Feeling (Fe).

Now we’ve established an INFJ’s first two functions:

  1. Ni (Introverted Intuition)
  2. Fe (Extraverted Feeling)

Note that the first two functions are opposite in every way. One is introverted while the other is extraverted. One (Fe) is a deciding function and the other (Ni) is a perceiving function. We call this dynamic a Complementary Relationship because the functions are opposite in every way. They completely complement each other. There are eight complementary relationships:

All eight complementary relationships above are opposite in every way, so they don't compete with each other at all.

Finding the 3rd Function

The dynamic of opposites is a little different when we get to the 3rd function. It's almost completely opposite to the 2nd but not quite!

  1. The third function is in the opposite attitude of the second function. In our INFJ example this would mean that our third function is introverted because our second is extraverted. This leaves us guessing between four possible introverted functions. It could be introverted sensing, intuition, thinking, or feeling. How to narrow it down further?
  2. The third function is the same kind of function (deciding or perceiving) as the second but not the same function. Using the INFJ example, the same kind of function would narrow our choices down to Thinking or Feeling because those are our deciding functions. But it's not the same function so we're left with Thinking. We already know the third function is introverted, so the third is then Introverted Thinking.

We call this kind of relationship that we just described between the 2nd and 3rd function an Antagonist Relationship. It's not completely complementary as the relationship between the 1st and 2nd because the 2nd and the 3rd, in our INFJ example, are both deciding functions. Since they are the same kind of function there is a bit of friction. They're both working on making a decision but in a different way.

There are only four possible Antagonistic Relationships:

Deciding Functions

Perceiving Functions

Finding the 4th Function

This one is easy. Our fourth function is antagonistic to the first. If you check the list above there is only one function that is antagonistic to Introverted Intuition, and it is Extraverted Sensing.

Our third functions is Introverted Thinking





We can figure out the rest from the following rules:

  • Compared to function 2, function 3 is always:
    • The opposite attitude (introverted/extraversion)
    • The same role (deciding/perceiving). This means that if the second function is a deciding function (thinking or feeling) the third is also deciding function. If the second function is a perceiving function (sensing or intuition) the third is also a perceiving function.
    • The opposite kind. For example, if the second function is Thinking then the opposite kind is thinking (or vis versa). If the second function is Intuition, then the opposite kind is
    • same role (deciding or perceiving) but it's a different kind. That is if the second function is Function number 3 is Ti (Introverted Thinking) because 3 is always opposite of 2 (Extraverted Feeling) in every way except that both are either deciding or perceiving functions.
  • Function number 4 is Se (Extraverted Sensing) because 4 is always opposite of 1 (Introverted Intuition) in every way except that both are either deciding or perceiving functions.

The last four are same as the first four except opposite in attitude:

We’re done!

Here’s the full functional stack for the INFJ:

  1. Introverted Intuition (Ni)
  2. Extraverted Feeling (Fe)
  3. Introverted Thinking (Ti)
  4. Extraverted Sensing (Se)
  5. Extraverted Intuition (Ne)
  6. Introverted Feeling (Fi)
  7. Extraverted Thinking (Te)
  8. Introverted Sensing (Si)

That all seems pretty convoluted, but once you work through the pattern several times it will become intuitive. There’s a beauty to all this. It’s like a dance of opposites and the dance floor is our consciousness. I hope this is helpful!