2014]: ‘Predictions and Primitive Ontology in Quantum Foundations: A

Amajor disagreement between different views about the foundations of quantummech-anics concerns whether for a theory to be intelligible as a fundamental physical theory it must involve a ‘primitive ontology ’ (PO), i.e. variables describing the distribution of matter in four-dimensional space–time. In this article, we illustrate the value of having aPO.Wedosoby focussingon the role that thePOplays for extractingpredictions froma given theory and discuss valid and invalid derivations of predictions. To this end, we investigate a number of examples based on toymodels built from the elements of familia