Abstract
Yellowstone National Park poses critical issues in biology and philosophy. Among these are (1) how to value nature, especially at the ecosystem level, and whether to let nature take its course or employ hands-on scientific management; (2) the meaning of natural as this operates in park policy; (3) establishing biological claims on th scale of regional systems; (4) the interplay of natural and cultural history, involving both native and European Americans; (5) and sociopolitical forces as determinants in biological discovery. Alston Chase's strident Playing God in Yellowstone is critized and used as a test of David Hull's naturalistic philosophy of biology. Biology and philosophy in Yellowstone ought to combine for an appropriate environmental ethic.