The following is an attempt to encapsulate the inner world of Ni as experienced by the INFJ. There are ready misperceptions about what an INFJ looks like on the outside. Perhaps connecting momentarily to their inner world will shed some light. The infj doesn't always look like much at all externally.
Ni is a vast expanse of internalized perceptions and paradoxes. Extroverted Feeling and Sensing are absorbed readily and exhaustively filling an ocean of impressions. Nothing is discarded. It is like going through an old attic, but resisting throwing anything out - I might need this later. There is an instinctual drive onward towards completing the entire pattern, and so the mind works piecing together one by one every fleeting image and idea. There is little distinction between self and other in this immediate nuanced perception of the outside world. The mind is the sea drawing in rivers from every source. There is no initial process of dismissal. Everything is embraced.
The INFJ has two conflicting sources to negotiate this expanse: the first is Ni, the second Ti. These present an underlying conflict. Ni does its work in silence, unaware, piecing, realigning, examining, projecting, viewing every angle to how these endless impressions may become coherent. When this succeeds and a vast store of things align, the impression is powerful, arresting the attention. It can however, be in err. Ti is safer but requires elements of dismissal. It can dismiss something necessary for the unknown pattern. This creates a powerful internal conflict as neither approach can adequately deal with this sea of paradox.
Because of these processes, the INFJ tends to be outwardly withdrawn and easily overwhelmed. At the same time there is an underlying strength that has come to terms with every possible scenario.