Perhaps the greatest challenge facing physicalism is to explain how conscious experience can be accounted for within the physicalist framework. Given these rough characterisations of physicalism, before setting out to address the problem posed by consciousness, there is some prior conceptual work that must be done. It is already recognised in the literature that there are several desiderata that a characterisation of what it is to be physical must meet in order for that characterisation to be suitable for debates in the philosophy of mind. Two-category ontologies admit both substances and properties. Remember that properties are the ways substances are and that substances are what bear properties. On this view, a property counts as physical just in case it is the sort of property that appears in the theories of physical science. The conception of the physical approach delivers seems to lack the level of specificity and determinateness that is required in order for such a characterisation to be informative.