 In addition to its role in the development of macroevolutionary theory and its influence on scientific research, the passive/driven distinction raises a number of philosophical issues. As noted already, the notion of a passive trend links up with a traditional set of questions about the role of chance or randomness in evolution (Millstein 2000). Indeed, the passive/driven distinction looks a lot like the distinction between random genetic drift and selection in population genetics. Drift could be construed as a passive trend in gene frequencies. Grantham (1999) argues that the notion of a passive trend points toward a certain sort of explanatory pluralism: a trend that is best explained as a stochastic phenomenon at the macro-level could receive a more deterministic explanation at a lower level, and those explanations need not conflict. Turner (2014) suggests that the notion of a passive trend poses a challenge to popular interventionist ideas about causal explanation. Explaining a trend by showing that it is passive could turn out to be a non-causal explanatory strategy.