Introverted Thinking

Introverted Thinking is one of the eight function-attitudes defined by Carl Jung. Thinking (T) is an outlook that focuses on looking at the world “impersonally” or “technically”, in terms of objects and how they work, which we can call the “mechanics” of things (including people), often with a focus on goals such as efficiency. People preferring it tend to think in terms of “true” or “false”.
An "introverted" attitude (i) indicates that this outlook generally draws from the individual; or the inner world of the "subject" (individual ego), instead of directly from the outer world of the environment.

So introverted Thinking (Ti) can be described as "an assessment of “correct/incorrect” (mechanical “truth”) by an individual/natural standard, where one turns inward to an internal “blueprint” of proper relationship between objects. The individual’s assessment of true/false (mechanics of the situation) will be determined by individual reflection.
Every type does this, but for types who prefer Ti, it will be their main form of decision-making, rather than an environmental standard of how things should work (Te), or more "personal" or "interpersonal" criteria (F). These types will be denoted in the type code by a "T" and a "P"; i.e. "xxTP"; the "P" pointing to the Perception function (S or N) as being what is extraverted, or attuned to the environment, and so, for balance, Thinking, as the "Judgment" function, will be introverted.
The types holding the function as "dominant" are ISTP and INTP, while for ESTP and ENTP, it is "auxiliary". (For FJ types, it is tertiary or inferior, and may also develop at some point in life).

Ti Characteristics

As compared to those that use Extraverted Thinking (Te), individuals that use the cognitive function of Introverted Thinking (Ti) tend towards the following:

• Uses a framework or set of principles and seeks internal consistency between the framework and decisions
• Seeks clarity and precision. Asks is the thinking right?
• More analytical and deep application of logic than extraverted thinking
• As it is an internal process, it is often not as visible
• Tends to be more process focused than outcomes focused
• Seeks elegance and simplicity of the framework or principles
• Can come across to others as theoretical and hair splitting by those who don't prefer the process