 Sahotra Sarkar attempts to define biodiversity “implicitly” as opposed to “explicitly” contrary to Maclaurin and Sterelny (Margules &amp; Sarkar 2007; Sarkar 2002, 2005; Sarkar &amp; Margules 2002). A concept is given an explicit definition if, and only if, there is a set of necessary and sufficient conditions for the satisfaction of the concept. For example, suppose we define the concept species phylogenetically in the following way: necessarily, something is a species if, and only if, it is a lineage between two speciation events or a speciation event and an extinction event (Ridley 1989). An implicit definition is different; the concept is defined by some rules or axioms in which the concept appears. So, Sarkar characterizes biodiversity as follows,