This is the single most important concept for you to grasp.
Without it, you cannot understand the power of the Tetrahedraverse concept!

"Nothing" : absence of thingness ("no thing")
"[No Thing]" absence even of the absence of thingness.

Most people, when trying to grasp the concept "nothing," tend to employ mental means that merely bring into existence other "things." For example:

"empty space" ("emptiness" of some sort),
"vacuum" (obviously still a "thing").
"lack of any things at all" (a state of thingness-absence)

None of these, nor any other attempt at similar ideas, is correct.

Now make the following effort, repeatedly, until you are simply STOPPED by the impossibility of doing what you have been asked to do. (It will feel strange, perhaps even frightening, and it will be hard to reproduce again. It gets easier with practice.)

Imagine every thing that constitutes our Universe, including the space between things, shrinking. (Run the Big Bang backwards.)
Keep squeezing all thingness into a smaller and smaller form, until you reach a stage where it becomes a point, without size or shape.
Now: remove it.

Note that for most people, doing this "leaves something behind" (your mental space, at least; some imaginary empty space). This is made a bit clearer by the following four-stage exercise:

Imagine a point sitting in an 'empty' background space.

1) Remove the point. (Background space remains)
2) Put back the point, and remove the background space. (Point remains. Harder to do, though.)
3) Put back the background space, and remove the point first, then remove the background space. (Fuzzy/Difficult, eh?)
4) Put them both back, and remove the background space, then remove the point.

This (#4) seems impossible, since in order to remove the point after you have removed that which would have been "left over" when you did, you badly want to mentally reinstate the background space, and we shall not let you do that.

These are the four exercises which, if practiced dedicatedly, MAY lead you to the concept that you need, which is this:

A state of [NoThing] is an absolutely (not just "mentally") forbidden situation. It is absolutely impossible to 'have [NoThing]'; to begin with. One may only have "something" — mentally, or, I propose, in reality.

I must warn some of you, and risk your opinion that I may simply be egomaniacal, by telling you: some of you may not be able to reach this starting point for Tetrahedraverse. The non-concept (or anti-concept) required may not be reachable by everyone, or even by many. In my experience, only by actually reaching the necessary concept, is it possible to tell whether or not you have reached it. The 'slamming into a wall' mental effect that betrays the presence of success is unambiguous, and you will know it if it happens, but you will have an awful time trying to word it so that I, or anyone else who's grasped this, can be certain that you have done it.

This is unfortunate, but simple mental inability to do the necessary thing in the mind seems to be the case with at least a few people, and probably with a lot of people. Evidence: I have been discussing this concept 'semi-live' (on echomail systems) for more than eight years, and in all that time, and with all those people, I have found it RARE that one of them understands this well enough to even begin to construct a firmly believed mental model of Tetrahedraverse. I'm sorry, but that's apparently just the way of it.

If you find that you cannot do it, then please stop reading about this, since it will either make no sense to you, or your journey with me will always have the property of "fuzzy doubt"; you will not have been able to agree that this is the only absolute/abstract way to make a Universe "from nothing." (Not-From [NoThing].)

We now may begin to establish, step by step, the "origin sequence" which leads inevitably and logically to "Tetrahedraverse."