  The aim of this paper is to introduce a new member of the family of the modal
interpretations of quantum mechanics. In this modal-Hamiltonian interpretation,
the Hamiltonian of the quantum system plays a decisive role in the
property-ascription rule that selects the definite-valued observables whose
possible values become actual. We show that this interpretation is effective
for solving the measurement problem, both in its ideal and its non-ideal
versions, and we argue for the physical relevance of the property-ascription
rule by applying it to well-known physical situations. Moreover, we explain how
this interpretation supplies a description of the elemental categories of the
ontology referred to by the theory, where quantum systems turn out to be
bundles of possible properties.
