  The long lasting discussion on the completeness of quantum theory (QT) has
not yet come to an end. The discussion is impeded by the lack of a clear
understanding of what makes up the contents of a theory of physics in general
and of QT specifically. After such an understanding has been developed, a more
precise definition of global properties, such as the completeness,
computability, and extensibility of a theory, is possible and necessary. This
paper addresses these subjects for theories of physics and, in particular, for
QT. The basis for the definition of the completeness of a theory is the
proposed definition of a "formal causal model of a physical theory". The formal
model can be applied to discussions of general attributes, such as
completeness, computability, and extensibility.
