 Mill’s methods and their generalized versions may even be viewed as providing some kind of a logic of discovery (see also Schaffner 1974), the existence of which has long been controversial (Nickles 1980). However, it should be noted that the methods of causal reasoning do not generate causal knowledge from scratch, as it were. They already take causal hypotheses as inputs and refine them in an iterative way (Grasshoff 2011). While some formulations (including Mill’s own mentioned above) may suggest that the inputs to Mill’s methods are mere associations or regularities, it should be clear by now that the method is only reliable if some kind of causal knowledge is already at hand. In our example above, the causal assumption is that of causal homogeneity, which obviously has causal content. This vindicates the slogan “no causes in, no causes out” (Cartwright 1989, Ch. 2).