The phrase Theory of Everything (TOE) is used in physics and cosmology to label a theory that encompasses all physics, generally used specifically to mean some future law that describes the four forces of nature, electromagnetism (in its quantum form), gravity (general relativity), the strong force, and the weak force. No current theory is generally accepted. Some theories of cosmology make the working assumption that there is such a connection between the forces, and that in the hot, dense early universe, the distinctions we currently perceive were not yet evident. Electroweak theory, developed in the 1950s-1970s, managed to explain both electromagnetism and the weak force. Earlier, culminating in the 19th century, electricity and magnetism were described by a single theory summarized by Maxwell's equations. Einstein famously persisted in attempting to find a unified field theory (UFT) that explained both gravitational and electromagnetic fields. The term Grand Unified Theory (GUT) is used for theories that explain both electroweak and the strong force, and the Theory of Everything would combine that with gravity. One type of theory that has been investigated for the last few decades as a candidate is string theory.