The causal powers of things are all dispositional properties, i.e. properties whose identities depend on what they dispose their bearers to do. But I do not think, as some philosophers do, that all properties are dispositional. Spatio-temporal relations, for example, may hold, without disposing their relata to do anything. Nevertheless, there is an important link between these relations and the causal powers that things may have, because the instances of the causal powers must all have categorical dimensions, i.e. spatio-temporal locations, distributions, and so on, which are definable only in terms of such relations. Formally, the structures definable wholly in terms of such relations are just quiddities, i.e. things whose identities depend on what they are—not on what they do. But this is not to say that they have no place in a realistic theory of what there is. For, if there were no quiddities in the world, there would be no causal powers. And, if the there were no causal powers, then the world itself would be just a quiddity.