In the INFP’s cognitive stack, Introverted Feeling comes first, then Extraverted Intuition, Introverted Sensing, and finally, Extraverted Thinking.
Now, having both “Ne” and “Si” so close to each other is somewhat unusual, only 1/4 of all personality types have “Ne” and “Si” as either 2nd and 3rd functions. And though 1/4 honestly isn’t rare, that just means that not many types have “Ne” and “Si” as more conscious functions together. Some types might have “Ne” as their first function and “Si” as their last, however, that last “Si” isn’t as developed as the “Ne”. So its unusual seeing both “Ne” and “Si” at almost the same levels of development.
Only INFPs and INTPs have their 2nd function as “Ne” and their 3rd function as “Si”.
ESTJs and ESFJs have their 2nd function as “Si” and their 3rd function as “Ne”.
Extraverted Intuition, as Cognitive Processes states, “involves noticing hidden meanings and interpreting them, often entertaining a wealth of possible interpretations from just one idea or interpreting what someone’s behavior really means.”
It focuses on the question of “what if?”, and it looks for every interpretation and possibility from every occurring event. Because of “Ne”, INFPs will be able to discern hidden patterns, details, potentials, and possibilities.
As Personality Junkie expresses, “Ne” “prompts extraverted exploration in an open-ended fashion.”
While INFPs desire inner, introspective exploration through “Fi”, they also seek outer exploration, seeking new ideas, interesting theories, adventure, anything that may spark a flame in their inner selves. We INFPs love the newness of an idea and seek ways of finding new ones in the world or ways of brainstorming new ones.
Below Extraverted Intuition on the cognitive stack is Introverted Sensing. If Extraverted Sensing cares very much about external details, Introverted Sensing also cares very much about internal details.
“Si” pays a lot of attention to how the INFP is feeling and to comparing current feelings, thoughts, experiences, to past memories. In many ways, the INFP seeks familiarity through “Si”, and because “Si” is the INFP’s third function, that also means that the INFP will be more comfortable and can relax through “Si”. So if things around the INFP feel familiar and aren’t too deviant from the INFP’s memories, then the INFP can relax.
So while “Ne” desires for new experiences and new ideas, “Si” seeks familiarity, physical comfort, and relaxation.
The INFP could be compared Bilbo Baggins from The Hobbit. Though Bilbo would rather stay at home, rest, and eat almost every hour of the day, he also feels drawn to having an adventure, as bothersome as they are.
As different as these two functions are, they are a good pair of functions for the INFP to possess.
As Personality Junkie says, “Ne” will often prompt “wandering” and seeking new experiences, however, “Si” is a reality check for the INFP. So while the INFP wants to explore, they also have learned from previous experience through “Si” what to do and what not to do.
Having both “Ne” and “Si” isn’t a hindrance either. Sometimes a new experience, though exciting, can be rough for the INFP who just needs some closure. From personal experience, if I’m in a new experience that makes me uncomfortable, I’ve noticed that I can gain some closure and relax a little when there’s some sense of familiarity, like having a friend alongside me.
Also, INFPs can be prone to go into hermit-like states where they just want to feel comfortable and relax from the stresses of life because of their “Si”. This harmful state of not going out into the world and living life can often be overcome through the INFP’s “Ne” which will spark a desire to go out and have new experiences.
So while “Si” makes sure that the INFP doesn’t do anything irrational when seeking adventure, “Ne” makes sure that the INFP doesn’t stay too long in the INFP’s comfort zone.