 While the policy context for conservation of biodiversity has maintained a core focus on variety (as reflected in the CBD and IPBES definitions), the more academic discussions are harder to pin down. Philosophical discussions about “biodiversity” illustrate the current lack of academic consensus on fundamental issues, including biodiversity’s definition, its value, and even its history. Increased popularity of the term among academics has amounted to decreased clarity of the term. If we look under “Definition of biodiversity” in the Encyclopedia of Biodiversity, we find that “An unequivocal, precise, and generally accepted definition of biodiversity does not exist” (Swingland 2013). The recent book, Defending Biodiversity (Newman, Varner, &amp; Linquist 2017) has the premise that it will be impossible to ever settle on a definition. This entry therefore will focus on these fundamental issues concerning biodiversity’s definitions and values. The particular focus is on the concept of variety (rather than the definition and value of individual elements such as species). Other biodiversity-related philosophical issues are covered in other SEP entries (see the supplementary document on  biodiversity preservation  in the entry on  environmental ethics,  and the entries on  conservation biology  and on  ecology).