Most people forget it is part of a system and by defining all the aspects of the system you can more clearly see the interactions and attributes of the functions. Anyway from an article I wrote a while ago:
Introverted Intuition - INTJ and INFJ
Foreseeing implications, transformations, and likely effects
As ever introverted intuition is an ill defined process. It is an introverted subconcious perceiving process thus leaving most bewildered at its function. It imaginatively creates benchmarks and using iconology determines the similarities in ideas proposing the implications of these ideas and how they can affect the world. It is also sneakily subjective as it lends to a person a censored thought pattern to others around them as the benchmarks and iconology may bear little relation to reality but subtle guide the definition of the introverted intuitive. Over time it is passively enriched by other functions as experience is gained.
For the INFJ the introverted intuition is supported by extroverted feeling as a way to deal with the need to protect the imaginative and uniquely defined benchmarks of the Ni mindset is reconciled with attempting to gain a mutual understanding of shared external space.
In contrast the INTJ supports introverted intution by protecting their mindset by logically critiqueing their external environment using thinking to select elements of the environment which suit their inner vision.