**Theory of Everything**

From time immemorial, man has desired to comprehend the complexity of Nature in terms of as few elementary concepts as possible. ~ Abdus Salam

Physicists have long sought an umbrella theory that explains and connects all known physical phenomena, along with the predictive power to anticipate the outcome of any experiment within the physical realm – in other words, the formula to make the world deterministic.

Archimedes was perhaps first in describing Nature by axiomatic principles and using them to deduce new results. The path of theoretical unification has been dreamt by many of his successors: Democritus, Newton, Laplace, Einstein, and others.

Some of the most recent attempts are string theory and M-theory, though those are more particularly oriented toward an approach for producing a unified theory, rather than being a completed theory unto themselves.

A pivotal struggle has been unifying the 3 forces understood at the quantum level (strong, weak, electromagnetism) with gravity, which is incidental at the quantum scale, but long proved tricky to bottle in equation form at that level, owing to the infinities that arise. Relativity reveals a bendable 4d spacetime, whereas quantum mechanics has treated spacetime as unrealistically rigid.

All unification theories suffer from the same philosophical problem: the barrier between the continuity of the field and the discreteness of the quantum. Any quantum-based theory of physical reality must explain everything in terms of the discrete nature of particles, while any relativity-based theory must proceed from the continuity of the spacetime structure. ~ American theoretical physicist James Beichler