I want to learn how the functions work together. For example, in an INFJ how does their Fe work with their Ni, Se and Ti. How can I go about learning this? I need to fully understand the functions. Being able to identify them isn't enough maybe?

Your correlating functions all work together. Ni takes in the facts of its physical environment through Se, and Ti adds logic to the people-pleasing Fe.

Your top two functions work together the strongest, which means for an INFJ, their Ni and Fe are working back and forth. Ni is figuring out stuff and processing huge amounts of information in order to come to a conclusion. (This is why INFJs are so “intellectual,” because they like feeding their dominant Ni information, so if they take an interest in something, 500 books later they’ll have the big picture and conclusion as to what it all means. Once they have absorbed all the information about it that they can get their hands on, and reached a conclusion about it… they’re done with it. Nothing new to learn here, move on!)

Fe both makes them amenable and enjoy helping and pleasing other people, and also gives them an INTEREST in PEOPLE in general. While INFJs share their INTJ cousin’s interest in new information, they will be much more drawn to information that relates in some way to people (history, psychology, etc), as opposed to Te’s interest in impersonal systems (mathematics, science, etc). INFJs have a natural ability to understand how people work (Ni-Fe) and a desire to know more about how people work (Ti). Ti makes them crave UNDERSTANDING – both of impartial systems (how does that pump valve work?) and other people (why did you just do that?).

That’s why so many INFJs breathe a sigh of relief when they discover the MBTI system – aha! At last! Not only do they understand themselves, and why they do what they do, but now they can understand why OTHER PEOPLE do what they do! It not only pleases their “gimme more information” Ni, it also pleases their Fe, because now they can live without passing such harsh judgments on other people’s behavior as much. No one is stupid, they are simply different and at unique levels in their functional maturity. Ni is happy with new information. Fe is delighted with anything that sheds a light on people. Ti now has a base format on which to analyze other people, so it is happy.

Se is the weakest element of the INFJ, but it functions in silence in the background. Less mature Se-users will be largely oblivious to their surroundings, because they are functioning totally in an internal imaginary world of information and ideas. (This is why INXJs have a tendency to walk into walls, trip over their own feet, or fall in holes.) But… Ni needs something in its environment to draw from, and Se provides that purpose. As an INFJ, you are using Se when you’re absorbing information from other people. It’s not your Ni alone giving you magical insights into people’s true motivations or feelings; it is Se, picking up on subtle physical signs and mannerisms. Se notices slight physical clues, which informs your Ni that “something more is going on here” than what comes out of someone else’s mouth. Ni then takes an intuitive leap and gives you the answer. If you use Ni alone in forming conclusions, you may be wrong – but once you involve Se, and base your assumptions about other people and situations on solid facts from behavior, you will right in your predictions most of the time, because Se is impartial. It doesn’t see what isn’t there. It sees eye movements, body language, micro-expressions, etc.

The unique combination of these functions are what make INFJs so sensitive. Their Se is picking up on what they aren’t consciously aware of, and their detached, ethereal Ni removes them as a physical being from the situation (that same “absence” that makes them so clumsy at times), which means their Fe takes over and allows them to feel what the people in the environment are feeling. Because it is so incredibly imaginative, Ni can run away with them if they don’t learn how to balance it using their Ti – to step back and analyze whether or not letting Ni-Fe invest them emotionally in a situation is wise. Often, they can’t help it, but they can learn to slow the process or even stop it afterward utilizing their Ti.

The combination of Ni and Se are also what make INFJs perfectionists, inclined to dislike the physical manifestation of their imagined reality – the book, piece of art, architecture, or reality is never as wonderful as the concept in their head. Se makes them appreciate beauty, but keenly aware of all their physical flaws. It makes them not like shabby-looking things, and have a secret desire for luxurious items and expensive taste. But because they are so lofty in their imagination, the INFJ often feels that it’s wrong to indulge Se too much, and deny themselves what they want, or feel guilty for buying pretty things that serve no real purpose. (If it’s pretty, and it makes you happy, and it didn’t cost you so much money that you’ll be eating dog food for the next week, it’s okay to buy it.)

Inferior functions, when used properly, can give any personality a chance to relax and rest from the continual use of their upper functions. INFJs can both mature their Se and relax their Ni when they do things that allow them to use it – gardening (noticing all the colors, and watching ladybugs), hiking, biking, traveling, photography… things that get them outdoors. The bottom line is that all your functions interact all the time, whether or not you’re aware of them. But some of them are weaker than others. You can work on strengthening Ti by asking how things work, and stopping to analyze a situation rather than being content merely to “feel” it. And you can strengthen Se by intentionally paying more attention to your environment.