Three proposals have been considered. The first, the mutual manipulability account, understands constitutive relevance in terms of the experimental manipulations used to test interlevel relations. According to this account, if it can be shown (i) that the putative components are contained within S, (ii) that some ideal interventions on the putative component (x’s φ-ing) change the phenomenon (S’s ψ-ing), and (iii) that some ideal interventions on S’s ψ-ing change x’s φ-ing, that is sufficient to establish that x is a component in the mechanism. The notion of an ideal intervention in this account is explicitly indebted to and a proposed extension of Woodward’s theory of causal relevance to the constitutive domain (see Craver 2007; see also Kaplan 2012). A concern with the mutual manipulability account, though, is that it is best an epistemic guide to constitutive relevance, not an account of what constitutive relevance is (Couch 2011). The account offers, at best, a sufficient condition of relevance. Also, the notion of an “ideal” intervention, borrowed from Woodward’s account of causal relevance, cannot be applied straightforwardly to constitutive explanations. An ideal intervention on a system cannot intervene on both the independent and the dependent variable at the same time. However, when one intervenes to make S ψ (or prevent S from ψ-ing), one invariably also intervenes on the components of S’s ψ-ing. And when one intervenes on the components of S’s ψ-ing, one often intervenes on S’s ψ-ing. Because x’s φ-ing and S’s ψ-ing are related as part to whole, they are not independent, and so require another way to think about ideal interventions (see Baumgartner 2010; 2013; Leuridan 2011; yet see Menzies 2012; Woodward 2014.