uses to be effective. Theory of Change as a concept has strong roots in a number of disciplines, including environmental and organizational psychology, but has also increasingly been connected to sociology and political science. Within industrial-organizational psychology, Austin and Bartunek have noted that approaches to organizational development are frequently based on more or less explicit assumptions about 1) the processes through which organizations change, and 2) the interventions needed to effect change. Development in evaluation practice Within evaluation practice, Theory of Change emerged in the 1990s at the Aspen Institute Roundtable on Community Change as a means to model and evaluate comprehensive community initiatives. Notable methodologists, such as Huey-Tsyh Chen, Peter Rossi, Michael Quinn Patton, Heléne Clark, and Carol Weiss, had been thinking about how to apply program theories to evaluation since 1980. The Roundtable's early work focused on working through the challenges of evaluating complex community initiatives. This work culminated in a 1995 publication, ‘New Approaches to Evaluating Comprehensive Community Initiatives’. In that book, Carol Weiss, a member of the Roundtable's steering committee on evaluation, hypothesized that a key reason complex programs are so difficult to evaluate is that the assumptions that inspire them are poorly articulated. She argued that stakeholders of complex community initiatives typically are unclear about how the change process will unfold and therefore place little attention on the early and mid-term changes needed to reach a longer-term goal. Weiss popularized the term “Theory of Change” as a way to describe the set of assumptions that explain both the mini-steps that lead to the long-term goal of interest and the connections between program activities and outcomes that occur at each step of the way. She challenged designers of complex community-based initiatives to be specific about the theories of change guiding their work and suggested that doing so would improve their overall evaluation plans and would strengthen their ability to claim credit for outcomes that were predicted in their theory. She called for the use of an approach that, at first glance, seems like common sense: lay out the sequence of outcomes that are expected to occur as the result of an intervention, and plan an evaluation strategy around tracking whether these expected outcomes are actually produced. Her stature in the field, and the apparent promise of this idea, motivated a number of foundations to support the use of this technique—later termed “the Theory of Change approach”—in