Most generally, a sympathy with the view that ultimately nothing resists explanation by the methods characteristic of the natural sciences. A naturalist will be opposed, for example, to mind-body dualism, since it leaves the mental side of things outside the explanatory grasp of biology or physics; opposed to acceptance of numbers or concepts as real but non-physical denizens of the world; and opposed to accepting real moral duties and rights as absolute and self-standing facets of the natural order. The central problem for naturalism is to define what counts as a satisfactory accommodation between the preferred sciences and the elements that on the face of it have no place in them. Alternatives include instrumentalism, reductionism, and eliminativism, as well as a variety of other antirealist suggestions (see realism/anti-realism). The term naturalism is sometimes used for specific versions of these approaches in particular areas: Moore, for example, defined naturalism in ethics as the doctrine that moral predicates actually express the same thing as predicates from some natural or empirical science. This suggestion is probably untenable, but as other accommodations between ethics and the view of human beings as just parts of nature recommend themselves, these then gain the title of naturalistic approaches to ethics. See also nature.