 Marie Kaiser (2011, 2015) has recently given a thorough analysis of reductive explanation, including a systematic treatment of metaphilosophical issues that underlie different approaches (see 2015, Chapter 2). Instead of arguing for or against reduction, she both articulates the advantages of an explanation being reductive and indicates that many biological phenomena cannot be explained in this way. On Kaiser’s account, an explanation is reductive if it has three characteristics: (1) lower-level, (2) internal, and (3) parts-in-isolation. “Lower-level” means that the explanation relies only on features that are at a lower level than the phenomenon being explained. Similar to Sarkar’s hierarchical account, a reduction does not have to be a molecular or lowest-level explanation because Kaiser wants to capture reductive explanations throughout biology, including ecology. Explanations with this characteristic provide an epistemically important unidirectional “flow” of explanation from the lower to the higher level, even if some of the relevant lower-level entities are not spatial parts of the explanandum phenomenon. However, Kaiser secondly requires that reductive explanations appeal only to physical parts (“internal”) of the explanandum phenomenon or system. Additionally, to fully qualify as reductive, an explanation must represent each part it invokes in isolation—not in isolation from any context, but rather in isolation from a part’s original complex context. This “parts-in-isolation” characteristic is associated with a system being near-decomposable; upon decomposition, a part’s actual functioning can be understood in isolation. The whole system’s operation then can be recomposed from the parts interacting in a largely sequential and linear fashion (Bechtel and Richardson 1993). Using these three characteristics, one can classify different explanations and distinguish a reductive explanation from a mechanistic explanation from a part-whole explanation (Kaiser 2015).