To outsiders, INTJs may appear to project an aura of "definiteness", of self-confidence. This self-confidence, sometimes mistaken for simple arrogance by the less decisive, is actually of a very specific rather than a general nature; its source lies in the specialized knowledge systems that most INTJs start building at an early age. When it comes to their own areas of expertise -- and INTJs can have several -- they will be able to tell you almost immediately whether or not they can help you, and if so, how. INTJs know what they know, and perhaps still more importantly, they know what they don't know.
INTJs are perfectionists, with a seemingly endless capacity for improving upon anything that takes their interest. What prevents them from becoming chronically bogged down in this pursuit of perfection is the pragmatism so characteristic of the type: INTJs apply (often ruthlessly) the criterion "Does it work?" to everything from their own research efforts to the prevailing social norms. This in turn produces an unusual independence of mind, freeing the INTJ from the constraints of authority, convention, or sentiment for its own sake.....