Theory of Change: A Path to Positive Social Impact for Engineers

Engineers are accustomed to working toward complex outcomes. We design systems that must function reliably under uncertainty, meet multiple constraints, and perform over long periods of time. We use models, logic, and decomposition to reason from high-level goals to concrete design actions. We are generally capable of working in this logical way for technical systems, but things become significantly more complicated when working on socio-technical systems. 

A Theory of Change (TOC) brings this same logical discipline to questions of social impact [1]. The following image provides the general notion of a TOC. The element types in this image are described later. 

Figure 1: An example of a Theory of Change. Diagram by the author.

At its core, a TOC is about establishing the logic that leads to a complex outcome. The process typically begins by envisioning a desired long-term impact and then working backward to identify the medium- and short-term outcomes, as well as activities and outputs that must occur for that long-term impact to plausibly be achieved [1, 2]. 

Rather than asking “What should we build?”, a TOC asks a more demanding question: '“Why do we believe change will happen – and how might our work contribute to it?”

Why Theory of Change Matters for Engineers 

Many engineers already think in ways that are compatible with a Theory of Change. Systems engineering, requirements decomposition, and verification planning all rely on explicit logical chains. 

What a TOC adds is a focus on human and social change, often unfolding over years rather than weeks or months [2]. When engineers engage with the TOC process, the focus is on human and social change as influenced by engineered systems operating within a broader socio-technical network. 

Why is this important? Engineers increasingly want their work to balance economic, environmental, and social impact. Yet social impact is rarely linear, immediate, or fully controllable. A Theory of Change provides a way to reason about this complexity without pretending it can be simplified away. 

The Structure of a Theory of Change 

Most Theories of Change are organized around a simple but demanding chain: 

Inputs → Activities → Outputs → Outcomes → Impact [2]

• Inputs are the resources required to act. 

• Activities are what engineers and designers do. 

• Outputs are the direct products of those activities. 

• Outcomes are changes in human/social condition that result. 

• Impact is the long-term, cumulative effect of many outcomes. 

The value of a TOC lies not in naming these elements, but in articulating why one plausibly leads to the next. 

Outputs vs. Outcomes (Where Most TOCs Fail) 

A critical distinction — and a common source of confusion — is the difference between outputs and outcomes [2, 3]:

Outputs are what we produce; outcomes are what change. Deploying a product is an output; changing daily behavior, access, or capability is an outcome. 

Outputs are largely under a team’s control. Outcomes are not. Social impact does not occur simply because outputs exist; it occurs when outputs change real-world conditions [2]. 

Example: A Theory of Change in Practice 

A clear example of a Theory of Change applied to a complex socio-technical challenge is provided by the Clean Cooking Alliance. Their published TOC explicitly maps activities to outputs, outputs to outcomes, and outcomes to long-term impact across health, gender equity, climate, livelihoods, and governance. Note that the outputs are the text shown on curves (arcs) in the image. Importantly, the figure illustrates not just a linear chain, but a systems-level view of how coordinated engineering, policy, financing, and user-centered activities must align over time to plausibly achieve impact.  

Figure 2: The Clean Cooking Alliance’s Theory of Change [4].

Outcomes, Indicators, and Credibility 

The outcomes of a Theory of Change must be observable to be meaningful. 

A credible TOC specifies outcomes with enough clarity that progress can be assessed. This often involves indicators that answer four questions: 

• Who or what is expected to change? 
• How many will change? 
• How much change is expected? 
• By when? 

This framing follows established Theory of Change practice and is central to outcome credibility [5]. This discipline forces teams to confront assumptions early, rather than discovering them after resources are spent. 

Outcome Pathways and Impact 

Individual outcomes do not stand alone. They form outcome pathways — connected sequences of change that must align in order to plausibly lead to impact [2]. 

If outcomes do not reinforce one another, the pathway weakens. 

This mirrors engineering logic: subsystem performance must align with system-level intent. A Theory of Change makes that alignment explicit socially, not just technically [6]. 

Engineering Impact Is Broader Than We Expect 

In social programs, outcomes are often framed primarily as behavioral change. In engineering, outcomes may also include changes in access, capability, risk, opportunity, and daily practice introduced by products and systems. 

Research on engineered products has shown that social impact spans many domains, including health, education, work, family life, equity, social connection, and cultural identity [7, 8]. Importantly, products rarely affect society in only one of these ways. 

This breadth reinforces the value of TOCs: it helps engineers reason about what might change, not just what will be built. 

Theory of Change as an Engineering Hypothesis 

For engineers and designers, a TOC is not a prediction. It is a hypothesis: a reasoned argument about how change might occur [1]. 

Used well, a good TOC helps teams: 

• Clarify assumptions 
• Align activities with intended impact 
• Identify weak or missing logic 
• Design with long-term consequences in mind 

In this way, Theory of Change becomes a natural extension of engineering thinking – a tool for designing not just products, but responsible pathways to real impact. 

References 

[1] Weiss, Carol H. “Nothing as Practical as Good Theory: Exploring Theory-Based Evaluation for Comprehensive Community Initiatives for Children and Families.” New Approaches to Evaluating Community Initiatives: Concepts, Methods, and Contexts, vol. 1, 1995, pp. 65-92.

[2] Rogers, Patricia. Theory of Change. UNICEF Methodological Briefs: Impact Evaluation, no. 2, 2014.

[3] Taston, Thomas M. “That’s an Output, Not an Outcome.” Medium, 2018, thomasmtaston.medium.com/thats-an-output-not-an-outcome-b34cf23eb734.

[4] Clean Cooking Alliance Theory of Change. Clean Cooking Alliance, Jan. 2024, cleancooking.org/wp-content/uploads/2024/01/Clean-Cooking-Alliance_Theory-of-Change.pdf.

[5] Taplin, Dana H., et al. Theory of Change. Technical Papers: A Series of Papers to Support Development of Theories of Change Based on Practice in the Field. ActKnowledge, 2013.

[6] Clark, Louise, and J. Marina Apgar. Unpacking the Impact of International Development: Resource Guide 1. Introduction to Theory of Change. Institute of Development Studies, 2019, hdl.handle.net/20.500.12413/14792.

[7] Mattson, Christopher A., et al. “Fifty-Five Prompt Questions for Identifying Social Impacts of Engineered Products.” Journal of Mechanical Design, vol. 146, no. 1, 2024, p. 011402.

[8] Rainock, Meagan, et al. “The Social Impacts of Products: A Review.” Impact Assessment and Project Appraisal, vol. 36, no. 3, 2018, pp. 230-41.

To cite this article:
Mattson, Chris. “Theory of Change: A Path to Positive Social Impact for Engineers.” The BYU Design Review, 17 December 2025, https://www.designreview.byu.edu/collections/theory-of-change.