Abstract
I explain Loophole Theory (LT) and show some applications of it. The basic element of LT is the truism that everything physical is physical. Any ontological domain that can be defined according to this template (everything X is X) is called a universe. LT allows causal relations between universes via the notion of interfaces. Interfaces are hypothetical domains that are not universes. The idea is that the one universe can be followed by another universe via an interface. Interfaces are defined as being composed of, at least, parts of two universes. Some examples could be the mind/body interface, the physical/mathematical interface and the something/nothing interface.