From what I've understood, the basic motivation behind the idea of "the Theory of Everything" (its modern attempt being M theory) is to find a simple rule which unifies all phenomena observed in nature. Ideally, although this may not be possible, we would be able to calculate/derive all fundamental physical constants directly from it instead of determining their values experimentally. Setting aside the question of how feasible this is, what I'd like to know is the following: How is the Theory of Everything supposed to take into account the complete initial conditions of the universe? By "complete initial condition", I'm referring to the perfect description of the configuration of all particles/energy values. Wouldn't the Theory of Everything, supplemented with such a theory of initial conditions be exceedingly ugly?

Once again, by "complete initial condition" I'm not referring to the values of certain basic parameters (like entropy) but rather the detailed configuration of literally everything that exists.

Also, if no such account can be expected, how do we know that the initial conditions are uniquely determined by the physical laws? And if not, what's the point of having a Theory of Everything when it nevertheless unable to explain why the initial configuration was the way it was.

I'm not a physicist but am interested in such matters. Thank you in advance!

  • $\begingroup$ theory.caltech.edu/people/jhs/strings/str143.html $\endgroup$ Commented Nov 17, 2017 at 14:45
  • $\begingroup$ You are assuming that the initial conditions were complex, such as an astronomical number of particles in various states. This assumption is inconsistent with the law of the entropy increase. Because entropy increases, it must have been the lowest at the beginning. And with no source of or reason for complexity at the very beginning, entropy must have started from zero (or some logical minimum). This implies a full symmetry with everything in a single state, absolute zero temperature, and very simple initial conditions. $\endgroup$
    – safesphere
    Commented Nov 17, 2017 at 18:02
  • $\begingroup$ Your second unclear assumption is that the physical laws somehow existed already at the beginning instead of being created along with the creation of matter. An ideal theory of everything would have to explain how the laws of nature came to existence as well. $\endgroup$
    – safesphere
    Commented Nov 17, 2017 at 18:06

1 Answer 1


The goal of a theory of everything TOE in physics is not what you are describing and expect.

A theory of everything (ToE), final theory, ultimate theory, or master theory is a hypothetical single, all-encompassing, coherent theoretical framework of physics that fully explains and links together all physical aspects of the universe.1:6 Finding a ToE is one of the major unsolved problems in physics. Over the past few centuries, two theoretical frameworks have been developed that, as a whole, most closely resemble a ToE. These two theories upon which all modern physics rests are general relativity (GR) and quantum field theory (QFT).

Maybe some of the constants could be eliminated by the unification but by no means the majority of them. The TOE will be predictive of new data, using values from all old data in the formation of the theory.

TOE was an idea which developed slowly as a the particle physics data started becoming accurate enough to be modeled with a specific Lagrangian, and it refers to the unification of all known forces, electromagnetic, weak, strong and gravitational.

The first unification happened when Maxwell unified electricity and magnetism into electrodynamics, which until then were considered separately.

The second unification of the weak with the electromagnetic was verified by the discovery of the Higgs boson at LHC, which veriefied the symmetry breaking mechanism at very large interaction energies.

At the moment the SU(3)xSU(2)xU(1) symmetry group of the standard model of particle physics, fits practically all measurements and is very predictive, it also uses a large number of constants taken from measurements and fits.

Indications for unification of all three, electromagnetic, weak , and strong exist in the measurements of the running coupling constants of the three interactions which indicate that at even higher energies all three interactions will depend on one coupling constant. This needs models beyond the standard model , called Grand Unified field Theories, GUT.

Various Gut models are under research, but still they cannot be a TOE because they do not include gravity. Gravity has not been definitively quantized which is necessary for a unified theory of everything.

There are various theoretical models of which imo string theory based ones have a good chance of success, because they can incorporate the standard model and all the data it has already fitted and also the quantization of gravity, but a definitive model is still in the research stage.

The initial conditions , once a TOE exist , will be fitted from cosmological observations, and then predictions for new observations will be made, which, if validated, will validate the TOE. Physics models are validated step by step.

  • $\begingroup$ This is a nice answer, but I would not say that the standard model 'unifies' the strong and electroweak forces, which remain distinct (if coupled) SU(3) and SU(2)xU(1) sectors. Proposals for strong--electroweak unification into a single (semi-)simple group are called Grand Unified Theories (GUTs), and would form another step on your path from Maxwell to string theory. $\endgroup$ Commented Nov 17, 2017 at 16:45
  • $\begingroup$ @DavidSchaich yes, you are correct but I was sloppy, I will correct. $\endgroup$
    – anna v
    Commented Nov 17, 2017 at 17:11

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