  Any complete theory of physical reality must allow for the ubiquitous
phenomenon of subjective experience at some level, or risk being conceptually
incoherent. However, as long as the ontological status of subjectivity itself
remains unresolved, the topic will be seen as more within the purview of
philosophy than of physics. Towards a resolution of this issue within
empirically motivated physical theory, this article introduces an operational
definition that ultilizes the general consensus that subjective mental states,
whatever else is controversial about them, at least correlate in some way to
physical states. It is shown here that implementing this underappreciated
assumption within the framework of a physical theory in fact leads to
wide-ranging consequences. In particular, a correlation requires there exist a
well-defined mapping from a space of subjective mental states onto a space of
information-bearing elements of some physical theory. Given the peculiar nature
of subjective states as inherently private appearances, any empirical
identification of states must be performed by the experiencing subject. It is
argued that such an operationally defined 'self-measuring' act leads
unavoidably to an 'uncertainty principle' that is analogous in some intriguing
ways to Heisenberg's principle for quantum mechanics. A model is then
introduced for subjective states as algorithmically incomputable numbers.
Additionaally, an inequality similar to Bell's theorem may be derived,
indicating an analogy with the violations of local reality and the ontology of
observables within quantum mechanics.
