Introverted Thinking is a right-brain form of judgement that makes us aware of a situation's many variables. When we use it, we recognize our power, as individuals, to exploit some variables at the expense of others. (...)
This kind of awareness is not only impersonal: it's graphic, immediate, and holistic. It prompts no predetermined categories of good and bad. Variables that have unusual or perverse potential are accorded the same consideration as variables that assure a socially appropriate outcome. (...)
As a right-brain function, Introverted Thinking is not conceptual and linear [contra Extraverted Thinking]. It's body-based and holistic. It operates by way of visual, tactile, or spatial cues, inclining us to reason experientially rather than analytically. (...)
Introverted Thinking (Ti) is the attitude that beneath the complexity of what is manifest (apparent, observed, experienced) there is an underlying unity: a source or essence that emerges and takes form in different ways depending on circumstances. What is manifest is seen as a manifestation of something. From a Ti standpoint, the way to respond to things is in a way that is faithful to that underlying cause or source and helps it emerge fully and complete, without interference from any notion of self. The way to understand that underlying essence is to learn to simultaneously see many relationships within what is manifest, to see every element in relation to every other element, the relationships being the "signature" of the underlying unity. This can only be experienced directly, not second-hand. (...)
Introverted Thinking is a form of mental representation in which every input, every variable, every aspect of things is considered simultaneously and holistically to perceive causal, mathematical, and aesthetic order. What you know by Ti, you know with your hands, your eyes, your muscles, even a tingling sensation "downstairs" because you sense that everything fits. Every variable is fair game to vary, every combination of variables worthy of consideration; the only ultimate arbiter is how well the parts form a unified whole rather than a jumble.
Orienting by Ti, you track causal harmony: you are part of the system, you do your part to fit in with that overall way that things make sense and harmonize. You get into "the flow" or "the zone". You need a gestalt sense of order to know what to do – a sense that you feel in your body, in your mind, in everything at once. "I get it." Without that, you are lost. (...)
For example: You hear a Brahms piece that you've never heard before, and you're sure it's Brahms. How can you tell? You can't name a criterion, like the pitch of the notes, the number of notes, or some simply measurable criterion like that (see extraverted thinking). You know "all at once" because of the way in which the notes all relate to each other. You sense the overall pattern as an indivisible gestalt way in which the music makes sense.
For example: You are composing a piece of music, and you sense that something "doesn't fit". A dominant seventh chord here just doesn't fit the style of the piece. You take it out and replace it with a peculiar series of ambiguous chords, bridging two sections of the piece in a way that leads to but doesn't give away what is to come. Ahh, now that's right. That's what the piece really wanted. It's not what "you" wanted, it's what the emerging causal harmony of the music wanted. "Your" only job is to create faithfully to that emerging harmony – to follow the groove.
What is that groove? What distinguishes the harmonious whole from the jumble, or the almost-whole? This cannot be said, it can only be pointed to. It cannot be defined in advance of knowing it. It cannot be defined separately from the physical material that it potentially exists within. You can "say" it only by directing someone's attention to the parts and how they fit together. You acquire terms of discourse – a vocabulary of things to say – only through "conversation" with the material itself: interacting with it, letting it take shape. Once you've found the groove, you can explore it endlessly – the infinity of ways in which the underlying Idea of the Whole necessitates the arrangement of the parts, the infinity of different ways that the same Idea can be realized in different parts and different situations, and what that Idea is.
In contrast to the "linear thinking" necessitated by extraverted thinking's representation in terms of verbally defined criteria, Ti takes in everything at once and converts it into a "way in which the whole fits together." You can't stop and explain each step as you go; there are no steps, only flow, only finding the groove and going with it. (...)
Introverted Thinking leads you to relate whatever you are doing to some larger principles that you have identified. Hence, Ti is like having some kind of book in your head, which describes the inner workings of things. When interacting with reality, you are constantly writing and re-writing your book. To deal with anything, you have to be able to understand in terms of the observations in your book. Whenever you are dealing with any new system, you start writing a new chapter on it in order to attain complete understanding of it.
This approach may seem very cumbersome from an extraverted standpoint. You don't really need to understand how a bicycle works in order to ride one. You don't have to actually understand a subject in school if you simply cram and memorize. You don't have to understand computers to check your email. Yet Ti leads you to desire complete understanding of whatever you are doing, instead of looking up the correct procedure, or asking your friends for help, or kicking it when it's not working. With Ti, you don't simply try to understand a system well enough to manipulate it. You try to become such an expert on how it works that you could write a book about it if you had to, even if your expertise is unusable or useless to everybody (sometimes even to yourself).
Hence, Ti is a kind of high-bandwidth understanding, because it leads you to try to understand the entire causal, aesthetic, or logical mechanism of any system of interest. This kind of understanding takes much more time and effort to develop, but it is more flexible once attained, because it allows you to deal with aspects of reality that cannot be described through social norms or sets of discrete procedures. (...)