  The term quantum logic has different connotations for different people,
having been considered as everything from a metaphysical attack on classical
reasoning to an exercise in abstract algebra. Our aim here is to give a uniform
presentation of what we call operational quantum logic, highlighting both its
concrete physical origins and its purely mathematical structure. To orient
readers new to this subject, we shall recount some of the historical
development of quantum logic, attempting to show how the physical and
mathematical sides of the subject have influenced and enriched one another.
