 According to epistemic norms shared implicitly by neuroscientists, good explanations in neuroscience are good mechanistic explanations; and good mechanistic explanations are those that pick out invariant relationships between mechanisms and the phenomena they control. (For fuller treatment of invariance in causal explanations throughout science, see James Woodward 2003. Mechanists draw extensively on Woodward’s “interventionist” account of cause and causal explanations.) Craver’s account raised questions about the place of reduction in neuroscience. John Bickle (2003) suggested that the working concept of reduction in the neurosciences consists of the discovery of systematic relationships between interventions at lower levels of biological organization, as these are pursued in cellular and molecular neuroscience, and higher level behavioral effects, as they are described in psychology. Bickle called this perspective “reductionism-in-practice” to contrast it with the concepts of intertheoretic or metaphysical reduction that have been the focus of many debates in the philosophy of science and philosophy of mind. Despite Bickle’s reformulation of reduction, however, mechanists generally resist, or at least relativize, the “reductionist” label. Craver (2007) calls his view the “mosaic unity” of neuroscience. Bechtel (2009) calls his “mechanistic reduction(ism)”. Both Craver and Bechtel advocate multi-leveled “mechanisms-within-mechanisms”, with no level of mechanism epistemically privileged. This is in contrast to reduction(ism), ruthless or otherwise which privileges lower levels. Still we can ask: Is mechanism a kind of reductionism-in-practice? Or does mechanism, as a position on neuroscientific explanation, assume some type of autonomy for psychology? If it assumes autonomy, reductionists might challenge mechanists on this assumption. On the other hand, Bickle’s reductionism-in-practice clearly departs from inter-theoretic reduction, as the latter is understood in philosophy of science. As Bickle himself acknowledges, his latest reductionism was inspired heavily by mechanists’ criticisms of his earlier “new wave” account. Mechanists can challenge Bickle that his departure from the traditional accounts has also led to a departure from the interests that motivated those accounts. (See Polger 2004 for a related challenge.) As we will see in  section 8 below,  these issues surrounding mechanistic philosophy of neuroscience have grown more urgent, as mechanism has grown to dominate the field.