Editing Theory of everything (section)

===Definition of fundamental laws===
There is a philosophical debate within the physics community as to whether a theory of everything deserves to be called ''the'' fundamental law of the universe.<ref>Weinberg (1993), Ch 2.</ref> One view is the hard [[reductionist]] position that the theory of everything is the fundamental law and that all other theories that apply within the universe are a consequence of the theory of everything. Another view is that [[emergence|emergent]] laws, which govern the behavior of [[complex system]]s, should be seen as equally fundamental. Examples of emergent laws are the [[second law of thermodynamics]] and the theory of [[natural selection]]. The advocates of emergence argue that emergent laws, especially those describing complex or living systems are independent of the low-level, microscopic laws. In this view, emergent laws are as fundamental as a theory of everything.

A well-known debate over this took place between Steven Weinberg and [[Philip Warren Anderson|Philip Anderson]].<ref>{{Cite book|title=Superstrings, P-branes and M-theory|page=7}}</ref>

====Impossibility of calculation====
Weinberg<ref>Weinberg (1993) p. 5</ref> points out that calculating the precise motion of an actual projectile in the Earth's atmosphere is impossible. So how can we know we have an adequate theory for describing the motion of projectiles? Weinberg suggests that we know ''principles'' (Newton's laws of motion and gravitation) that work "well enough" for simple examples, like the motion of planets in empty space. These principles have worked so well on simple examples that we can be reasonably confident they will work for more complex examples. For example, although [[general relativity]] includes equations that do not have exact solutions, it is widely accepted as a valid theory because all of its equations with exact solutions have been experimentally verified. Likewise, a theory of everything must work for a wide range of simple examples in such a way that we can be reasonably confident it will work for every situation in physics. Difficulties in creating a theory of everything often begin to appear when combining [[quantum mechanics]] with the theory of [[general relativity]], as the equations of quantum mechanics begin to falter when the force of gravity is applied to them.