 A sympathetic reconstruction of the position under discussion might go as follows. On an interventionist account of causation, causes (whether we think of them as events, types of events, properties, facts, or what have you) must be representable by means of variables—where this means, at a minimum, that it must be possible for the cause to change or to assume different values, for whatever object, unit or system those values are assigned to, as when it is possible for the same particle to be either at position \(p_1\) specified by a position variable \(P\) or at some alternative position \(p_2\). This is required if we are to have a well-defined notion of manipulating a candidate cause and well-defined answers to counterfactual queries about what would happen if the cause were to be manipulated in some way—matters which are central to what causal claims mean on any version of a manipulability theory worthy of the name. However, for some putative causes, there may be no well-defined notion of change or variation in value and if so, a manipulability theory will not count these as genuine causes. Suppose, for example, we lack any coherent conception of what it is for something to exist but to be non-physical. Then there will be no well-defined notion of intervening to change whether something is or is not a physical object and being a physical object will not be a factor or property that can serve as a cause. (Of course it is consistent with this that there are true and perhaps even lawful generalizations about all physical objects.). For example, although to the best of our knowledge, it is a law of nature that 