The view that the real world is nothing more than the physical world. The doctrine may, but need not, include the view that everything that can truly be said can be said in the language of physics. Physicalism is opposed to ontologies including abstract objects, such as possibilities, universals, or numbers, and to mental events and states, in so far as any of these are thought of as independent of physical things, events, and states. Whilst the doctrine is widely adopted, the precise way of dealing with such difficult customers is not agreed. Nor is it entirely clear how capacious a physical ontology can allow itself to be, for while physics does not talk in terms of many everyday objects and events, such as chairs, tables, money, or colours, it ought to be consistent with a physicalist ideology to allow that such things exist. Some philosophers believe that the vagueness of what counts as physical, and the vagueness of what counts as incorporating such things into a physical ontology, make the doctrine vacuous. Others believe that it forms a substantive metaphysical position. One common way of framing the doctrine is in terms of supervenience. Whilst it is allowed that there are legitimate descriptions of things that do not talk of them in physical terms, it is claimed that any such truths about them supervene upon the basic physical facts. However, supervenience has its own problems.