Introverted Thinking is this: a is true because b is true because c is true because d is true etc..

Introverted Thinking is structure: pure, unadulterated structure. It only has to do with math in as much as it can structure sequences of Extraverted Thinking relationships between numbers.

Introverted Thinking says that something is true because something else is true. If you were to take this to its logical conclusion, then the world is true because everything in it is true.

"I think, therefore I am."

Anything else is not Introverted Thinking, but rather Introverted Thinking accompanied by another function. Most people don't know the difference, nor can you if you do not accept exertion theory as true. (there again, Introverted Thinking)

You might say that Introverted Thinking truths are only true because they are interconnected by Extraverted Thinking. But the two are probably inseperable.
I agree with the general sentiment, but there is more to it than just this.

I agree that Ti is the discrete relation between two facts. "follows from" seems to be one incarnation. I think there are more, but that is besides the point.

What is important, is that the actual truth of Ti-spawned relations is never self-sustaining, while the IXTj often makes it sound as if it is. Take the words you wrote that I have quoted; you seem convinced that they are true, and yet, you state no proof for them. You couldn't give proof if you wanted to. I can't prove what I write here either, and yet we both feel we speak on behalf of 'the truth'. How does that work?

Here is my theory: Ti unites converging 'subjective experiences'. It identifies what Fe units have in common and groups them together, it unites them under the same banner. It appeals to others to explore their subjective experiences on a subject, and points out where those experiences agree. What they agree on, then becomes a self-evident truth, begging to be upheld and built upon.

In my views, every function is strongly tied to it's dual-seeking counterpart. One is defined internally by it's connection to individual units of the other.