 Those who favor teleological theories of content usually favor an etiological theory of functions, according to which an item’s function is determined by its history of selection or by past selection of things of that type. Roughly, on an etiological theory of functions, an items function is what it was selected for, or what things of the type were selected for (see, e.g., Millikan 1989a and Neander 1991; important precursors are Ayala 1970 and Wright 1973, 1976). This idea can be spelled out in different ways. One influential proposal stems from Karen Neander, who gives the following definition for functions in physiology: