A third approach to constitutive relevance dispenses with the interlevel framing enforced by the mutual manipulability account and attempts to analyze relevance using causal notions only. According to accounts of this sort, constitutive relevance is a kind of causal between-ness. If S’s ψ-ing is understood as an input-output relationship of some sort, then mechanistic relevance could be understood as being a necessary link in the causal chain between the input and the output (see Harinen forthcoming; Menzies 2012). The putatively interlevel experiments in the mutual manipulability account can then be recast as different kinds of unilevel causal experiments. Romero (forthcoming) provides a helpful framing of these issues and offers the novel suggestion that putatively high-level interventions are in fact fat-handed interventions relative to their lower-level counterparts.