  Five physical assumptions are proposed that together entail the general
qualitative results, including the Born rule, of non-relativistic quantum
mechanics by physical and information-theoretic reasoning alone. Two of these
assumptions concern fundamental symmetries of physical interactions. The third
concerns the Hilbert-space dimensions and the fourth and fifth the
self-interaction Hamiltonians of the systems that function as "observers"
within the theory. These assumptions are shown to provide a sufficient
motivation for the usual Hilbert-space formalism, and to obviate the
observation-related axioms and most interpretative assumptions with which
minimal quantum mechanics is typically supplemented.
