 Some philosophers’ definitions of natural selection are clearly intended to capture this focused usage of the term. Millstein, for instance, characterizes selection as a discriminate sampling process (Millstein 2002: 35). Otsuka identifies natural selection with the causal influence of traits on offspring number in causal-graphical models (Otsuka 2016: 265). Okasha interprets the covariance of offspring number and offspring phenotype as quantifying the causal influence of selection (Okasha 2006: 28) Clearly, these uses of “natural selection” are meant to capture only an element of Darwin’s process; they make no mention of inheritance or replication. As discussed further below, controversies over the focused notion of selection have to do with whether the focused notion of selection can be distinguished from that of drift  (section 3),  and whether selection, in the focused sense, should be counted as a cause  (section 5).