  In contrast to the Copenhagen interpretation we consider quantum mechanics as
universally valid and query whether classical physics is really intuitive and
plausible. - We discuss these problems within the quantum logic approach to
quantum mechanics where the classical ontology is relaxed by reducing
metaphysical hypotheses. On the basis of this weak ontology a formal logic of
quantum physics can be established which is given by an orthomodular lattice.
By means of the Soler condition and Piron's result one obtains the classical
Hilbert spaces. - However, this approach is not fully convincing. There is no
plausible justification of Soler's law and the quantum ontology is partly too
weak and partly too strong. We propose to replace this ontology by an ontology
of unsharp properties and conclude that quantum mechanics is more intuitive
than classical mechanics and that classical mechanics is not the macroscopic
limit of quantum mechanics.
