  Is it possible to encompass the full extent of the universe within a theory
based on a finite set of first principles and inference rules?
  The r\^{o}le of observers and observations in physics theories is considered
here in the light of G\"{o}del's incompleteness theorem. Physics theories are
the sum-total that we -- humans, scientists, physicists -- can make in
interpreting our observations of the universe. We are integral part of the
universe, together with our observations, therefore acts of observation are
also observables and should become part of the phenomena considered by the
theory, especially in view of the fact that arbitrarily chosen modes of
observations may essentially determine empirical results.
  Incompleteness arises in G\"{o}del's theorem with self-referential
propositions. Observations and interpretations are acts of referencing, and
self-referencing occurs in physics whenever the observer is recognized as being
part of the observed system. If self-reference appears in physics in simile to
G\"{o}del's theorem, then incompleteness seems unavoidable in physics.
  The article discusses observers and observations as referencing in physics,
culminating with the understanding that they are hierarchically inter-related
so that a universal physics theory cannot be complete.
