Environmental science presupposes value judgements. Calls for sound, objective science are examined in the context of the US Endangered Species Act (ESA) and the controversy that surrounds the listing of Preble's mouse as a 'threatened' subspecies. Following an overview of this debate, its status as a controversy that can be resolved by objective knowledge alone is problematised by examining the normative underpinnings of species classifications, divergent risk orientations as they apply to concerns over classificatory errors, and the stating of testable hypotheses. Gleaning insights from the discussion, policy-relevant suggestions are provided.