Thread by @EricRWeinstein

1/ "Theories of Everything": A Taxonomy.

It is often said that "Theories-of-Everything are a dime a dozen" or that "All theoretical physicists worth their salt have several in a drawer." So far as I can tell, this is simply untrue. We've barely ever, if at all, seen candidates.

2/ The Escher Lithograph used in the first tweet points to the core of why TOEs are rare. A candidate TOE has to have some quality of "a fire that lights itself", which is difficult to think about beyond the equations that would instantiate it. Hence very few such theories exist.

3/ I'm going to lean on the following dictionary of analogies:

Physical Paper = Void
Pictured Canvas = Manifold and/or Einsteinian Spacetime
Ink=Matter & non-gravitational force fields
Pencils = Pre-Conscious Lego (e.g. amino acids)
Hands = Consciousness
Paradox = Self-awareness

4/ In my taxonomy, Type I TOEs are our least ambitious but they best match our state of the world. They are distinguished by two *separate* sources of origin: one for the Canvas (General Relativity or Witten's point i) ) & one for the Ink (Standard Model or Witten's point ii) ).

5 Type II TOE's are more ambitious & seek to derive the Ink from the choice of a mathematically distinguished Canvas that is anything but blank. My arch-nemesis @garrettlisi's theory is Type II. E8 is his 248 dimensional canvas. The intricacy is there, but doesn't quite match up.

6/ In Type III TOEs the ink is to be derived from canvas, but the canvas is essentially blank; it simply permits mathematics to happen (e.g. calculus and linear algebra). In such theories the ink has to be bootstrapped into existence. My lectures on Geometric Unity were Type III.

7/ Type IV TOE's try to change the question from Einstein's "Unified Field Theory." In String Thy, "Quantizing Gravity" became substituted for "Unified Field." For this crowd, many are now betting that the canvas & ink are both *emergent* from some deeper fundamental quantum thy.

8/ Type V TOEs are of a type I've never been able to fully contemplate; they are without boundaries or origins. There is no "Why is there something rather than nothing" within them. That which is not forbidden is compelled into existence. Void creates canvas & canvas begets void.

9/ Type VI TOEs begin with the hands. Religions are of this type. I pass over this in silence as they aren't scientific.

I will leave open higher types, but I've really only seen attempts at I-IV & I wouldn't call String-Thy/M-Thy a full TOE try since events of the last 15 yrs.

10/ I believe fundamental physics is stalled out because we are finally at the doorstep of a TOE and we haven't really bothered to think about what that would actually mean because we've never been here before. A final step need not look like any previous one. In fact, it cannot.

END/ My bet is on Type III for a reason:

Type I is not unified.
Type II is possible, but appears to be unworkable in details.
Type IV appears to lack sufficient guidance from Quantum theory to actually 'ship' despite consuming resources for yrs.
Types V & VI lack any progress.