  n this paper, we review and connect the three essential conditions needed by
the collapse model to achieve a complete and exact formulation, namely the
theoretical, the experimental, and the ontological ones. These features
correspond to the three parts of the paper. In any empirical science, the first
two features are obviously connected but, as is well known, among the different
formulations and interpretations of non-relativistic quantum mechanics, only
collapse models, as the paper well illustrates with a richness of details, have
experimental consequences. Finally, we show that a clarification of the
ontological intimations of collapse models is needed for at least three
reasons: (1) to respond to the indispensable task of answering the question
`what are collapse models (and in general any physical theory) about?'; (2) to
achieve a deeper understanding of their different formulations; (3) to enlarge
the panorama of possible readings of a theory, which historically has often
played a fundamental heuristic role.
