I want to explore the whole process of integrating the first three functions but first I want to think a little about the actual personality types. I have to eventually do a post, or maybe a page, on Jungian psychology, but I want to write a quick sketch of his thinking, both for any visitors but also for my own integration of these concepts.
Introversion and extroversion
First off, there are two basic attitudes that everyone falls into, introversion and extroversion. Jung's concepts of introversion and extroversion are so widespread they don't need much introduction but, for the sake of precision, I'd like to clarify what Jung meant. It's most commonly thought of as the divide between the kind of people who like to go to parties and those who prefer staying at home. Which may be true, but it's more accurate to talk about the flow of libido; one's energy and attention.
The extrovert is the easiest to understand - their energy and attention flow outwards, toward the outer world of things, people and ideas out there. They're the easiest to understand and the easiest to see because where their energy and attention is flowing is clear to anyone observing them. An introvert, on the other hand, spends most of their time and attention focusing on feelings, thoughts, etc. that are inside of them. The difference between the two may become more clear after looking at Jung's four functions and how each function differs when expressed by an introvert and by an extrovert.
Jung's four functions ("personality types")
There are 4 different functions in a personality, although everyone has one that's strongest, which is the one they're the most identified with, so the functions are commonly thought of as distinct personality types. The four functions are:
Thinking A person identified with the thinking function excels at manipulating ideas. Philosophers and theoretical physicists are your typical introverted thinkers; their main focus is on the ideas within them. Their concern is more about creating systems for understanding. Lawyers and experimental physicists, on the other hand, typify extroverted thinking; they care more for ideas as they apply to the "real world" (where an introverted thinker probably feels like their inner world is more real). Extroverted thinkers use their thinking to organize, codify and understand the world outside of them.
Sensation Someone primarily identified with the sensation function excels at manipulating objects. Engineers are often extroverted sensation types; they're the hard nosed realists who only believe in what they can see and feel with their five senses. Some may even take it to such an extreme that they even deny the reality of ideas. Introverted sensation types are also primarily concerned with the physical world but where extroverted sensation types focus on the things themselves, introverted sensation types are more concerned with the impact the world makes on themselves, on their inner worlds. I sometimes get flashes of what it's like to be an introverted sensation type when become completely absorbed in all the sensations and impressions while cooking, or biking; everything affects you deeply and the world itself becomes sacred.
Intuition Intuition is another function that's difficult to describe, and that's because it's main focus is in potential; an intuitive knows things without knowing how they know it. This is because the intuition comes out of the subconscious, from all the information that's constantly being collected there - intuitives have an innate, instinctive ability to access the subconscious. Extroverted intuitives are those entrepreneurs who can somehow sniff out the next big thing, before anyone else has even heard of it. Introverted intuitives are your typical shaman or medium, getting flashes of knowing from within.
Feeling If thinking types have a subtle and mature grasp of thinking, and sensation types of the physical world, feeling types have a subtle, mature and nuanced grasp of interpersonal relationships. Extroverted feeling types are those people who have an instinctive facility for understanding and working with others. Introverted feeling types are also most focused on their relationships, but they're more concerned with how those relationships are impacting them, as opposed to getting others to behave in a certain way. These are the people who can be at a party and say or do nothing but a calm good cheer spreads out from them like rings in water into which a stone has dropped (or, if they're in a bad mood, they can have the opposite effect on everyone.)
So, in a nutshell, extroverts focus on the outer world while their internal world is "merely" symbolic of what they feel is the real world of things and people. For introverts, however, their internal world is the focus of their energy and attention. The outer world is important mainly in how it provides grist for the inner mill.
Integrating the four functions
Archetypes, astrology and Jung's functions (oh my!)