  Even advocates of the mechanistic perspective have argued that it needs to be amended to accommodate the complex causal processes involved in cancer’s etiology. For instance, according to Bechtel (forthcoming), a linear picture of mechanisms for cancer leaves out an important dimension. He characterizes the mechanisms associated with apoptosis, for instance, as made up of two types: “primary” and “control” mechanisms. Failure to respond to signals promoting apoptosis in cancer may be a result of disruption in either one (or both) such mechanisms. Advocates of the mechanistic perspective have failed, Bechtel argues, to attend to the complex negative feedback processes of control and constraint affecting primary mechanisms. As evidence of the significance of such control mechanisms, he points out how cancer researchers utilize novel methods, such as network analysis to identify regulatory networks or feedback loops, associated with specific functions. Bechtel’s distinction between “primary” and “control” mechanism raises some interesting questions about the organization of causal pathways in cancer. Whether such pathways are, for instance, relatively fixed or static in organization, is an open question. Moreover, the category of “controller” versus “primary” mechanism itself may be relatively fluid, or context dependent. The “same” mechanism in a different environment might exert different controls, and, control mechanisms may themselves be viewed as primary, given one’s characterization of the function that is the subject of inquiry. 