Few topics are as important or contested as the relationships among capitalism, human wellbeing and ecological integrity. In her article "Can capitalism deliver environmental justice?" (Bell 2015 Environ. Res. Lett. 10 125017), Bell uses a seven-country comparison to explore how capitalism can either constrain or enable efforts to achieve environmental justice. This is an important contribution to these long-standing and recently re-ignited debates but also reminds us of the methodological challenges inevitably facing scholars attempting to engage with the big questions of capitalism and justice. Specifically the ambiguous and ideologically contested characteristics of these subjects leave scholars facing a series of hard decisions about how to operationalize studies and how to do so in ways that will be seen as credible and relevant even to those across ideological aisles.

Few topics are as important or contested as the relationships among capitalism, human wellbeing and ecological integrity. In recent years both public movements, such as the "Occupy Wall Street" protests and academic discourse, such as Piketty's high-profile book "Capital" (Piketty 2014), have reignited long-standing debates about human inequality within capitalist systems. Simultaneously, there has been a rapid increase in "green growth" discourse that emphasizes the potential for economic growth and ecological integrity to co-exist. A multitude of reports have been released exploring potential pathways towards "green growth" (Hallegatte et al 2012, World Economic Forum 2013), and several of these have included a consideration on inequalities. For instance, in 2012 China and the World Bank jointly released a report featuring "inclusive green growth" (World Bank and People's Republic of China 2012). Similar claims were articulated during the lead-up to the Paris 2015 climate negotiations by a prominent multi-stakeholder report entitled, "Better Growth; Better Climate: The New Climate Economy" (Global Commission on the Economy and Climate 2014).

While the green growth discourse is gaining traction within policy circles, many have critiqued it as inadequate and misguided (Caprotti and Bailey 2014, Tienhaara 2014), or destructive due to its potential to co-opt and disarm critiques of capitalism that would otherwise result in fundamental change (e.g. Kosoy et al 2012, Brown et al 2014). Bell's study, "Can capitalism deliver environmental justice?" (Bell 2015), is placed at the heart of debates about the possibilities and implications of attempts to harness capitalism to address human inequalities and ecological destruction.

Bell is interested in exploring how capitalism can either constrain or enable efforts to achieve environmental justice. Accordingly she embarks on an ambitious study of the intersection of environmental justice and capitalism across Cuba, South Korea, Bolivia, the United States, the United Kingdom, Sweden and China. These countries were chosen because each has seen attempts to achieve environmental justice, and because they represent a spectrum of state-market forms.

This research is part of a larger study (see Bell 2014) although this paper includes only interview data emerging from 140 interviews, roughly 20 in each country over a period of six years. These interviews included academics, activists, politicians and policy makers. Unlike many studies focused on either capitalism or environmental justice, this article starts from the fundamental premise that they are intrinsically interconnected, and thus attempts a more holistic exploration.

Overall Bell makes two key arguments. First, she notes that environmental injustices appear to be extremely persistent, regardless of the extent of marketization. Second, she notes that although all places have faced challenges in achieving progress towards environmental justice, there appears to be more space for more profound changes in those countries with greater resistance to capitalism, such as in Bolivia.

The core question spurring Bell's study could not be better timed but the subject of analysis is both amorphous and ideologically divisive which raises methodological complications. Those attempting to study capitalism's relationship with justice have to face several non-trivial challenges if they want to produce evidence that will be seen as credible and thought provoking to the diversity of stakeholders invested in these questions.

The first challenge is definitional. Both "environmental justice" and "capitalism" are multi-faceted, ambiguous concepts. As Bell notes, there is an ongoing conversation about the meanings of both terms, and a strength of the study is the explicit identification of three separate components of environmental justice: substantive, distributive and procedural. While other scholars have defined the dimensions somewhat differently (Fraser 2001, Schlosberg 2007) a multi-dimensional framework facilitates transparency and precision across separate elements of inherently complex and contested concepts.

However, identifying facets of these concepts does not entirely solve the methodological problems raised by their ambiguity. A related problem is that neither these concepts, nor their facets, have natural metrics. Instead scholars must make a choice. Either they can define some "objective" metrics (recognizing the limitations of such choices), or they can focus on how stakeholders embedded in specific contexts identify the concepts. These choices yield very different analyses of either capitalism or environmental justice, making systematic evaluation difficult.

In her study Bell has attempted to bridge these options by establishing widely accepted definitions of environmental justice and capitalism, and then using indepth interviews in each country to contextualize both concepts. Unfortunately, this choice has a downside. Relying on a handful of interviews per country does not adequately represent the explicitly spatial and contextual experiences of environmental justice. It also runs into the second major challenge facing work in this area – the ideologically contested nature of capitalism.

Few subjects could be more ideologically loaded than capitalism. Exploring an explicitly contested issue necessarily demands awareness about whose voices are privileged and whose are excluded from any analysis. A benefit of using qualitative data, such as in Bell's study, is that it allows individual voices to be heard in a way that is not possible through highly aggregated quantitative data. This is an appropriate strategy for dealing with deeply normative and contested subjects but comes at a cost. While statistical representation is not necessarily a requirement for this kind of work, it is essential that the selected interviews adequately cover the full depth of the issue from a wide diversity of perspectives. In such contested terrain, any hints of a non-transparent or predetermined study design will rapidly erode its credibility, especially to those who may not already agree with the researcher's core propositions. This need for depth necessarily limits the scope of any one study. Bell's study pushes her chosen methodology to, and probably beyond, its capabilites. However, for all its limitations, it places the onus on other scholars to do better in a fraught arena.

As with other heavily contested areas, there is a tendency for scholarship about both capitalism and environmental justice to remain internally focused within communities partially defined by their sympathies with particular positions. Unfortunately, keeping the conversation internal limits the ability for research to feed into the very transformations it often calls for. Genuinely transforming systems that are deeply embedded in every aspect of society is likely to demand very wide engagement and social discussion. This is not a time to preach only to the choir.

Scholars interested in contributing to the big debates raised by capitalism, human wellbeing and ecological integrity face a series of hard decisions. Do we shy away from the inherent methodological complications big questions raise, or do we work with admittedly incomplete but functional operationalizations? How do we research capitalism and justice in ways that encourages dialogue 'across the aisles' so that our insights are considered visible, credible, and relevant to a broader range of academics, policy-makers, and publics? These questions are unlikely to be resolved anytime soon, but remain as timely for scholars today as they were for Marx.

For references, see The challenges of studying capitalism and its discontents at environmentalresearchweb's sister journal ERL.