Book: My True Type, page 58 - 69

• Primary roles: To collect conscious and subconscious information, then synthesize it to produce impressions, insights, answers, and theories; to see deep causes, patterns, and laws underlying sense data
• Most prominent in: INTJs & INFJs; also prominent in ENTJs & ENFJs
• Associated with: Deep perceptiveness and insight, deep “knowing,” theoretical genius, powers of analysis and focus, advising and troubleshooting
• Famous INJs: Plato, Jesus, Nietzsche, Jung, Steven Hawking

Ni is the rarest of the eight types of functions, considered to have "signals of the universe". They are skilled at seeing the “dark skies before the storm.”

Ni likes to learn the "iceberg" of the problem

Reference

Book: My True Type Clarifying Your Personality Type, Preferences & Functions Copyright © 2014 A.J. Drenth