Introverted Intuitives have an incredibly rich inner dream world, in which they are bombarded by visions that constitute possibilities. The IN is usually fascinated by their daydreams, and likes nothing better than being a spectator in the world of their own mind. They constantly walk a line between these rich visions and the real world around them. If they walk that line successfully, they're capable of great things. Jung believed that Introverted Intuitives have access to the wisdom of all human history—that they have a private line to the Collective Unconscious.
The IN's daydreams are often visceral and attention-grabbing, but also objective and somewhat random, without obvious meaning. It's only when the IN applies judgement to their visions that they begin to understand them as real life possibilities, as something that can be attached to their own life experience. The Introverted Intuitive often wants to suspend judgement, to just experience the lovely images and ideas, but without a well-developed judgement function, these vision ideas are shallow and not related to any meaning or even to the IN's life outside of their mind. It is therefore important for the IN to consciously exert some judgement over their ideas. In this case, a little goes a long way, and the Introverted Intuitive need not fear the judgement.
Introverted Intuitives often choose careers in which they can make order from their store of ideas. They're typically quite intelligent and could choose from any number of professions, but they choose to be artists, writers, or scientists, or something that allows them to translate complex theories into something tangible.
Introverted Intuitives are known to be private, even stand-offish and difficult to get to know well. They tend to keep a handful of people close to them, and keep everyone else at arm's length, sometimes through an acerbic tongue or open hostility. It's difficult for the Introverted Intuitive to process a lot of external sensory data and stay true to the main goal of their type—vision perception—and perhaps that explains their reluctance to get close to others.
Typically, the few people who are close to the IN are very important to them, and the IN will be careful to treat them well. Sometimes, under stress or special duress, the inner life of the IN may appear so blissfully attractive, and it may seem so much easier for the IN to sit back and enjoy the inner-perception movie than to deal with the real world, where decisions must be made, external data must be processed, and partners must be appeased. In such cases, when the IN turns inward for its needs for intimacy, they are sending a powerful rejection message to their partner, and it may serve them well in the long run to remember that many studies have shown that people live longer, happier lives if they have a primary relationship with someone other than themself. It may be wise for the Introverted Intuitive to find an acceptable way to communicate their need for space or alone time.
Jung's Introverted Intuitive type was divided into two MBTI types by Isabel Briggs Myers:
INTJ - the Scientist, and INFJ - the Protector.
Check out the other Jungian types