“…As noted, ToCs are used in many theory-based evaluation approaches, such as realist evaluation and contribution analysis. Contribution analysis (CA) (Mayne, 2001(Mayne, , 2009(Mayne, , 2011(Mayne, , 2012a) is increasingly being used in evaluations of interventions in order to address the perennial challenge of "dealing with causality, " particularly in complex systems where changes in outcomes are the result of a number of factors in addition to the intervention-that is, situations where there are several factors acting together to bring about change, with each factor being a contributory cause and none being sufficient on its own to bring about the desired change (Mayne, 2012a; see also Buckley, 2016;Buregeya, Brousselle, Nour, & Loignon, 2017;Delahais & Toulemonde, 2017;Downes, Novicki, & Howard, 2018;Kane, Levine, Orians, & Reinelt, 2017;Mayne, 2012b;Noltze, Gaisbauer, Schwedersky, & Krapp, 2014;Terrapon-Pfaff, Gröne, Dienst, & Ortiz, 2018;and Ton, 2017. The aim is to make credible causal claims about the contribution an intervention is making to observed results. CA argues that if one can verify or confirm a theory of change with empirical evidence, 1 then it is reasonable to conclude that the intervention in question has made a difference.…”