The covering law model also fails to distinguish models that merely re-describe the phenomenon in general terms from explanations that, in addition to predicting aspects of the phenomenon, reveal the mechanisms that produce it (Craver 2006; Kaplan and Craver 2011; but see Weiskopf 2011). For example, Snell’s law allows one to predict how light bends when passing from one medium to another, but it does not explain why the light bends. New mechanists also argue that the covering law model fails to distinguish predictively adequate but fictional models from explanatory models. Finally, mechanists argue that the intertheoretic model of reduction fails to capture an important dimension of explanatory quality: depth. An implication of the covering law model is that any true law statements that allow one to derive the explanandum law (with suitable corrections and assumptions) will count as a complete explanation. Yet it seems one can deepen an explanation by opening black boxes and revealing how things work down to whatever level one takes as relatively fundamental for the purposes at hand. Such criticisms suggest that the covering-law model of constitutive explanation is too weak to capture the norms of explanation in the special sciences.