However, even if this general line of argument is accepted, there is room for differing views about exactly what its denial of ontological separateness requires. Let us agree that causes are “events” (or “facts”) that involve instantiations of  properties.[6]  So, if some special cause is not ontologically separate from some physical cause, the property instantiations that it involves cannot themselves be ontologically separate from the property instantiations involved in the physical cause. At this point, however, there are divergent views about how tight a constraint this imposes.